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Kreis C, Schmitz JR, Merkt F. High-Resolution Photoelectron Spectroscopy of the Ground and First Excited Electronic States of MgXe . J Phys Chem A 2024; 128:3149-3157. [PMID: 38619915 PMCID: PMC11056989 DOI: 10.1021/acs.jpca.4c00940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/17/2024]
Abstract
We report on the characterization of the X+ 2Σ+ ground and the A+ 2ΠΩ (Ω = 1/2, 3/2) and B+ 2Σ+ electronically excited states of MgXe+. Rotationally cold MgXe in the a 3Π0(v″ = 0) metastable electronic state was generated in a laser-ablation supersonic-beam source. Following single-photon excitation from the metastable state, the vibrational structure of the X+ state of MgXe+ was measured by pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy, and the adiabatic ionization energy of the X+ ← a ionizing transition was determined to be EI/(hc) = 37,468.3(6) cm-1. Spectra of the A+ ← X+ and B+ ← X+ transitions were recorded by using the method of isolated-core Rydberg-dissociation spectroscopy. The observation of the Mg+(3p) 2P1/2 + Xe 1S0 dissociation limit enabled the determination of the dissociation energies of the X+ [D0(X+) = 2970(7) cm-1] and A+ states [D0(A1/2+) = 9781(7) cm-1 and D0(A3/2+) = 9603(7) cm-1]. We compare these results with those of earlier experimental studies and ab initio quantum-chemical calculations.
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Affiliation(s)
- C. Kreis
- Institute of Molecular Physical Science, ETH Zurich, Zurich CH-8093, Switzerland
| | - J. R. Schmitz
- Institute of Molecular Physical Science, ETH Zurich, Zurich CH-8093, Switzerland
| | - F. Merkt
- Institute of Molecular Physical Science, ETH Zurich, Zurich CH-8093, Switzerland
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2
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Scheidegger S, Merkt F. Precision-Spectroscopic Determination of the Binding Energy of a Two-Body Quantum System: The Hydrogen Atom and the Proton-Size Puzzle. Phys Rev Lett 2024; 132:113001. [PMID: 38563947 DOI: 10.1103/physrevlett.132.113001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 01/18/2024] [Accepted: 01/25/2024] [Indexed: 04/04/2024]
Abstract
Precision measurements in Rydberg states of H with principal quantum number n in the range between 20 and 30 are reported. In the presence of homogeneous electric fields with strengths below 2 V cm^{-1}, these Rydberg states are subject to a linear Stark effect with accurately calculable Stark shifts. From the spectral positions of field-independent and field-dependent Rydberg-Stark states, we derive the n=20 and 24 Bohr energies, and the ionization energy with respect to the 2 ^{2}S_{1/2}(f=0,1) [short 2S(0,1)] metastable states. Combining these results with the 2S(1)-1S(1) transition frequency [C. G. Parthey et al., Phys. Rev. Lett. 107, 203001 (2011)PRLTAO0031-900710.1103/PhysRevLett.107.203001; A. Matveev et al., Phys. Rev. Lett. 110, 230801 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.230801] and the 1S hyperfine splitting [L. Essen et al., Nature (London) 229, 110 (1971)NATUAS0028-083610.1038/229110a0], we determine the ionization frequency of the 1S(0) ground state to be 3 288 087 922 407.2(3.7)_{stat}(1.8)_{syst} kHz, which is the most precise value ever determined for the binding energy of a two-body quantum system. Using the 2S(0)-2P_{1/2}(1) interval [N. Bezginov et al., Science 365, 1007 (2019)SCIEAS0036-807510.1126/science.aau7807], we determine the Rydberg frequency to be cR_{∞}=3 289 841 960 204(15)_{stat}(7)_{syst}(13)_{2S-2P} kHz in a procedure that is insensitive to the value of the proton charge radius. These new results are discussed in the context of the proton-size puzzle.
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Affiliation(s)
- Simon Scheidegger
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich 8093, Switzerland
- Quantum Center, ETH Zurich, Zurich 8093, Switzerland
| | - Frédéric Merkt
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich 8093, Switzerland
- Quantum Center, ETH Zurich, Zurich 8093, Switzerland
- Department of Physics, ETH Zurich, Zurich 8093, Switzerland
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3
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Doran I, Hölsch N, Beyer M, Merkt F. Zero-Quantum-Defect Method and the Fundamental Vibrational Interval of H_{2}^{+}. Phys Rev Lett 2024; 132:073001. [PMID: 38427875 DOI: 10.1103/physrevlett.132.073001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/29/2023] [Accepted: 01/12/2024] [Indexed: 03/03/2024]
Abstract
The fundamental vibrational interval of H_{2}^{+} has been determined to be ΔG_{1/2}=2191.126 614(17) cm^{-1} by continuous-wave laser spectroscopy of Stark manifolds of Rydberg states of H_{2} with the H_{2}^{+} ion core in the ground and first vibrationally excited states. Extrapolation of the Stark shifts to zero field yields the zero-quantum-defect positions -R_{H_{2}}/n^{2}, from which ionization energies can be determined. Our new result represents a 4-order-of-magnitude improvement compared to earlier measurements. It agrees, within the experimental uncertainty, with the value of 2191.126 626 344(17)(100) cm^{-1} determined in nonrelativistic quantum electrodynamic calculations [V. Korobov, L. Hilico and J.-Ph. Karr, Phys. Rev. Lett. 118, 233001 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.233001].
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Affiliation(s)
- I Doran
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - N Hölsch
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - M Beyer
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - F Merkt
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
- Department of Physics, ETH Zurich, Zurich, Switzerland
- Quantum Center, ETH Zurich, Zurich, Switzerland
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Clausen G, Scheidegger S, Agner JA, Schmutz H, Merkt F. Imaging-Assisted Single-Photon Doppler-Free Laser Spectroscopy and the Ionization Energy of Metastable Triplet Helium. Phys Rev Lett 2023; 131:103001. [PMID: 37739364 DOI: 10.1103/physrevlett.131.103001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/21/2023] [Accepted: 08/14/2023] [Indexed: 09/24/2023]
Abstract
Skimmed supersonic beams provide intense, cold, collision-free samples of atoms and molecules and are one of the most widely used tools in atomic and molecular laser spectroscopy. High-resolution optical spectra are typically recorded in a perpendicular arrangement of laser and supersonic beams to minimize Doppler broadening. Typical Doppler widths are nevertheless limited to tens of MHz by the residual transverse-velocity distribution in the gas-expansion cones. We present an imaging method to overcome this limitation that exploits the correlation between the positions of the atoms and molecules in the supersonic expansion and their transverse velocities, and thus their Doppler shifts. With the example of spectra of (1s)(np) ^{3}P_{0-2}←(1s)(2s) ^{3}S_{1} transitions to high Rydberg states of metastable triplet He, we demonstrate the suppression of the residual Doppler broadening and a reduction of the full linewidths at half maximum to only about 1 MHz in the UV. Using a retroreflection arrangement for the laser beam and a cross-correlation method, we determine Doppler-free spectra without any signal loss from the selection, by imaging, of atoms within ultranarrow transverse-velocity classes. As an illustration, we determine the ionization energy of triplet metastable He and confirm the significant discrepancy between recent experimental [G. Clausen et al., Phys. Rev. Lett. 127, 093001 (2021)PRLTAO0031-900710.1103/PhysRevLett.127.093001] and high-level theoretical [V. Patkós et al., Phys. Rev. A 103, 042809 (2021)PLRAAN2469-992610.1103/PhysRevA.103.042809] values of this quantity.
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Affiliation(s)
- Gloria Clausen
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Simon Scheidegger
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Josef A Agner
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hansjürg Schmutz
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
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5
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Herburger H, Wirth V, Hollenstein U, Merkt F. Pulsed-ramped-field-ionisation zero-kinetic-energy photoelectron spectroscopy of the metastable rare-gas atoms Ar, Kr and Xe. Phys Chem Chem Phys 2023; 25:22437-22454. [PMID: 37581215 PMCID: PMC10445426 DOI: 10.1039/d3cp02881j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 07/24/2023] [Indexed: 08/16/2023]
Abstract
The photoionisation of the metastable rare-gas atoms Rg = Ar, Kr and Xe is investigated at the Rg+ […](ns)2(np)5 2P3/2 ← Rg[…](ns)2(np)5((n + 1)s) 13P2 photoionisation threshold (n = 3, 4 and 5 for Ar, Kr and Xe) using the technique of pulsed-ramped-field-ionisation zero-kinetic-energy (PRFI-ZEKE) photoelectron spectroscopy. This technique, which monitors the field ionisation of high Rydberg states induced by a slowly growing electric-field ramp after a prepulse of opposite polarity, was recently introduced to record photoelectron spectra with high resolution and high sensitivity [Harper, Chen, Boyé-Péronne and Gans, Phys. Chem. Chem. Phys., 2022, 117, 9353]. A tunable UV laser system with a bandwidth of 30 MHz is used here to establish the factors determining the resolution and overall accuracy of this new method. In particular, the effects of stray electric fields, and of the magnitude of the prepulse and the field ramp on PRFI-ZEKE photoelectron spectra are studied by combining experiments with numerical simulations of the field-ionisation of high Rydberg states and of the electron flight times from the ionisation spot to the detector. A spectral resolution of 0.05 cm-1 is demonstrated in the photoelectron spectrum of metastable Ar.
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Affiliation(s)
- Holger Herburger
- Institute for Molecular Physical Science, ETH Zürich, 8093 Zürich, Switzerland.
| | - Vincent Wirth
- Institute for Molecular Physical Science, ETH Zürich, 8093 Zürich, Switzerland.
| | - Urs Hollenstein
- Institute for Molecular Physical Science, ETH Zürich, 8093 Zürich, Switzerland.
| | - Frédéric Merkt
- Institute for Molecular Physical Science, ETH Zürich, 8093 Zürich, Switzerland.
- Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
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6
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Martins FBV, Zhelyazkova V, Osterwalder A, Merkt F. Cold Ion-Molecule Chemistry: The Very Different Reactions of He⁺ with CO and NO. Chimia (Aarau) 2023; 77:221-224. [PMID: 38047800 DOI: 10.2533/chimia.2023.221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 02/28/2023] [Indexed: 12/05/2023] Open
Abstract
The ion-molecule reactions He+ + CO → He + C+ + O and He+ + NO → He + N+ + O have been measured at collision energies between 0 and kB · 10 K. Strong variations of the rate coefficients are observed below kB · 5 K. The rate of the He+ + CO reaction decreases by ~30% whereas that of the He+ + NO reaction increases by a factor of ~1.5. These observations are interpreted in the realm of an adiabatic-channel capture model as arising from interactions between the ion charge and the dipole and quadrupole moments of CO and NO. We show that the different low-energy behavior of these reactions originates from the closed- vs. open-shell electronic structures of CO and NO.
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Affiliation(s)
| | | | - Andreas Osterwalder
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Institute for Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich
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7
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Zhelyazkova V, Martins FBV, Schilling S, Merkt F. Reaction of an Ion and a Free Radical near 0 K: He + + NO → He + N + + O. J Phys Chem A 2023; 127:1458-1468. [PMID: 36752385 PMCID: PMC9940198 DOI: 10.1021/acs.jpca.2c08221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The reactions between ions and free radicals are among the fastest chemical reactions. They are predicted to proceed with large rates, even near 0 K, but so far, this prediction has not been verified experimentally. We report on measurements of the rate coefficient of the reaction between the ion He+ and the free radical NO at collision energies in the range between 0 and ∼ kB·10 K. To avoid heating of the ions by stray electric fields, the reaction is observed within the large orbit of a Rydberg electron of principal quantum number n ≥ 30, which shields the ion from external electric fields without affecting the reaction. Low collision energies are reached by merging a supersonic beam of He Rydberg atoms with a supersonic beam of NO molecules and adjusting their relative velocity using a chip-based Rydberg-Stark decelerator and deflector. We observe a strong enhancement of the reaction rate at collision energies below ∼kB·2 K. This enhancement is interpreted on the basis of adiabatic-channel capture-rate calculations as arising from the near-degenerate rotational levels of opposite parity resulting from the Λ-doubling in the X 2Π1/2 ground state of NO. With these new results, we examine the reliability of broadly used approximate analytic expressions for the thermal rate constants of ion-molecule reactions at low temperatures.
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8
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Kreis C, Holdener M, Génévriez M, Merkt F. High-resolution photoelectron spectroscopy of the ground and first excited electronic states of MgKr +. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2152746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- C. Kreis
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - M. Holdener
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - M. Génévriez
- Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - F. Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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9
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Perrin A, Orphal J, Huet T, de Natale P, Merkt F, Schlemmer S, Quack M, Willitsch S. Editorial. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2101246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Agnès Perrin
- Laboratoire de Météorologie Dynamique/IPSL, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Sorbonne Université, Ecole Normale Supérieure, PSL Research University, F-91120 Palaiseau, France
| | - Johannes Orphal
- Division 4 “Natural and Built Environment”, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany
| | - Thérèse Huet
- University of Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers, Atomes et Molécules, F-59000 Lille, France
| | - Paolo de Natale
- CNR-INO - Istituto Nazionale di Ottica, Largo Enrico Fermi 6, 50125 Firenze FI, Italy & LENS - European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino FI, Italy
| | - Frédéric Merkt
- ETH Zurich, Laboratory for Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Stephan Schlemmer
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
| | - Martin Quack
- ETH Zurich, Laboratory for Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Stefan Willitsch
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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10
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Agner JA, Albert S, Allmendinger P, Hollenstein U, Hugi A, Jouy P, Keppler K, Mangold M, Merkt F, Quack M. High-resolution spectroscopic measurements of cold samples in supersonic beams using a QCL dual-comb spectrometer*. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2094297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Affiliation(s)
- Josef A. Agner
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | - Sieghard Albert
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | | | - Urs Hollenstein
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | | | | | - Karen Keppler
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | | | - Frédéric Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | - Martin Quack
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
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11
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Zhelyazkova V, Martins FBV, Merkt F. Multipole-moment effects in ion-molecule reactions at low temperatures: part III - the He + + CH 4 and He + + CD 4 reactions at low collision energies and the effect of the charge-octupole interaction. Phys Chem Chem Phys 2022; 24:16360-16373. [PMID: 35762649 PMCID: PMC9258730 DOI: 10.1039/d1cp05861d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present experimental and theoretical studies of the He+ + CH4 and He+ + CD4 reactions at collision energies in the kB·(0-10) K range. Helium atoms in a supersonic beam are excited to a low-field-seeking Rydberg-Stark state and merged with a supersonic beam of CH4 or CD4 using a curved surface-electrode deflector. The ion-molecule reactions are studied within the orbit of the helium Rydberg [He(n)] electron, which suppresses stray-electric-fields-induced heating and makes it possible to reach very low collision energies. The collision energy is varied by adjusting the velocity of the He(n) atoms with the surface deflector, keeping the velocity of the methane beam constant. The reaction product ions (C(H/D)p+ with p∈ {1,2,3}) are collected in a time-of-flight mass spectrometer and monitored as a function of the collision energy. No significant energy-dependence of the total reaction yields of either reactions is observed. The measured relative reaction rate coefficient for the He+ + CH4 reaction is approximately twice higher than the one for the He+ + CD4 reaction. The CH+, CH2+ and CH3+ (CD+, CD2+ and CD3+) ions were detected in ratios 0.28(±0.04) : 1.00(±0.11) : 0.11(±0.04) [0.35(±0.07) : 1.00(±0.16):0.04+0.09-0.04]. We also present calculations of the capture rate coefficients for the two reactions, in which the interaction between the charge of the helium ion and the octupole moment of the methane molecule is included. The rotational-state-specific capture rate coefficients are calculated for states with J = (0-3) at collision energies below kB·15 K. After averaging over the rotational states of methane populated at the rotational temperature of the supersonic beam, the calculations only predict extremely weak enhancements (in the order of ∼0.4%) of the rate coefficients compared to the Langevin rate constant kL over the collision-energy range considered.
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Kreis C, Hollenstein U, Merkt F. Threshold-ion-pair-production spectroscopy of H 2S and D 2S. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2071349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- C. Kreis
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - U. Hollenstein
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - F. Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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13
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Beyer M, Merkt F. Structure and dynamics of HD + in the vicinity of the H + + D and D + + H dissociation thresholds: Feshbach resonances and the role of g/u-symmetry breaking. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2048108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Maximilian Beyer
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
- Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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14
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Zhelyazkova V, Martins FBV, Žeško M, Merkt F. Multipole-moment effects in ion-molecule reactions at low temperatures: part II - charge-quadrupole-interaction-induced suppression of the He + + N 2 reaction at collision energies below kB·10 K. Phys Chem Chem Phys 2022; 24:2843-2858. [PMID: 35050290 PMCID: PMC8809083 DOI: 10.1039/d1cp04798a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 12/23/2021] [Indexed: 11/22/2022]
Abstract
We report on an experimental and theoretical investigation of the He+ + N2 reaction at collision energies in the range between 0 and kB·10 K. The reaction is studied within the orbit of a highly excited Rydberg electron after merging a beam of He Rydberg atoms (He(n), n is the principal quantum number), with a supersonic beam of ground-state N2 molecules using a surface-electrode Rydberg-Stark decelerator and deflector. The collision energy Ecoll is varied by changing the velocity of the He(n) atoms for a fixed velocity of the N2 beam and the relative yields of the ionic reaction products N+ and N2+ are monitored in a time-of-flight mass spectrometer. We observe a reduction of the total reaction-product yield of ∼30% as Ecoll is reduced from ≈kB·10 K to zero. An adiabatic capture model is used to calculate the rotational-state-dependent interaction potentials experienced by the N2 molecules in the electric field of the He+ ion and the corresponding collision-energy-dependent capture rate coefficients. The total collision-energy-dependent capture rate coefficient is then determined by summing over the contributions of the N2 rotational states populated at the 7.0 K rotational temperature of the supersonic beam. The measured and calculated rate coefficients are in good agreement, which enables us to attribute the observed reduction of the reaction rate at low collision energies to the negative quadrupole moment, Qzz, of the N2 molecules. The effect of the sign of the quadrupole moment is illustrated by calculations of the rotational-state-dependent capture rate coefficients for ion-molecule reactions involving N2 (negative Qzz value) and H2 (positive Qzz value) for |J, M〉 rotational states with J ≤ 5 (M is the quantum number associated with the projection of the rotational angular momentum vector J⃑ on the collision axis). With decreasing value of |M|, J⃑ gradually aligns perpendicularly to the collision axis, leading to increasingly repulsive (attractive) interaction potentials for diatomic molecules with positive (negative) Qzz values and to reaction rate coefficients that decrease (increase) with decreasing collision energies.
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Affiliation(s)
| | | | - Matija Žeško
- Laboratory for Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Frédéric Merkt
- Laboratory for Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
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15
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Merkt F, Höveler K, Deiglmayr J. Reactions of H 2, HD, and D 2 with H 2+, HD +, and D 2+: Product-Channel Branching Ratios and Simple Models. J Phys Chem Lett 2022; 13:864-871. [PMID: 35045261 PMCID: PMC8802320 DOI: 10.1021/acs.jpclett.1c03374] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
We present measurements of the product-channel branching ratios of the reactions (i) HD+ + HD forming H2D+ + D (38.1(30)%) and HD2+ + H (61.9(30)%), (ii) HD+ + D2 forming HD2+ + D (61.4(35)%) and D3+ + H (38.6(35)%), and (iii) D2+ + HD forming HD2++ D (60.5(20)%) and D3+ + H (39.5(20)%) at collision energies Ecoll near zero, i.e., below kB × 1 K. These branching ratios are compared with branching ratios predicted using three simple models: a combinatorial model (M1), a model (M2) describing the reactions as H-, H+-, D-, and D+-transfer processes, and a statistical model (M3) that relates the reaction rate coefficients to the translational and rovibrational state densities of the HnD3-n+ + H/D (n = 0, 1, 2 or 3) product channels. The experimental data are incompatible with the predictions of models M1 and M2 and reveal that the branching ratios exhibit clear correlations with the product state densities.
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Affiliation(s)
- Frédéric Merkt
- Laboratorium für
Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
| | - Katharina Höveler
- Laboratorium für
Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
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Quack M, Abel B, Merkt F, Hippler H, Vöhringer P, Wodtke A, Willitsch S. Preface to the special issue: The beauty of chemical reaction kinetics, a Festschrift in honour of Jürgen Troe. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1984706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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17
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Zhelyazkova V, Martins FBV, Agner JA, Schmutz H, Merkt F. Multipole-moment effects in ion-molecule reactions at low temperatures: part I - ion-dipole enhancement of the rate coefficients of the He + + NH 3 and He + + ND 3 reactions at collisional energies Ecoll/ kB near 0 K. Phys Chem Chem Phys 2021; 23:21606-21622. [PMID: 34569565 PMCID: PMC8494273 DOI: 10.1039/d1cp03116c] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/02/2021] [Indexed: 11/29/2022]
Abstract
The energy dependence of the rates of the reactions between He+ and ammonia (NY3, Y = {H,D}), forming NY2+, Y and He as well as NY+, Y2 and He, and the corresponding product branching ratios have been measured at low collision energies Ecoll between 0 and kB·40 K using a recently developed merged-beam technique [Allmendinger et al., ChemPhysChem, 2016, 17, 3596]. To avoid heating of the ions by stray electric fields, the reactions are observed within the large orbit of a highly excited Rydberg electron. A beam of He Rydberg atoms was merged with a supersonic beam of ammonia using a curved surface-electrode Rydberg-Stark deflector, which is also used for adjusting the final velocity of the He Rydberg atoms, and thus the collision energy. A collision-energy resolution of about 200 mK was reached at the lowest Ecoll values. The reaction rate coefficients exhibit a sharp increase at collision energies below ∼kB·5 K and pronounced deviations from Langevin-capture behaviour. The experimental results are interpreted in terms of an adiabatic capture model describing the rotational-state-dependent orientation of the ammonia molecules by the electric field of the He+ atom. The model faithfully describes the experimental observations and enables the identification of three classes of |JKMp〉 rotational states of the ammonia molecules showing different low-energy capture behaviour: (A) high-field-seeking states with |KM| ≥ 1 correlating to the lower component of the umbrella-motion tunnelling doublet at low fields. These states undergo a negative linear Stark shift, which leads to strongly enhanced rate coefficients; (B) high-field-seeking states subject to a quadratic Stark shift at low fields and which exhibit only weak rate enhancements; and (C) low-field-seeking states with |KM| ≥ 1. These states exhibit a positive Stark shift at low fields, which completely suppresses the reactions at low collision energies. Marked differences in the low-energy reactivity of NH3 and ND3-the rate enhancements in ND3 are more pronounced than in NH3-are quantitatively explained by the model. They result from the reduced magnitudes of the tunnelling splitting and rotational intervals in ND3 and the different occupations of the rotational levels in the supersonic beam caused by the different nuclear-spin statistical weights. Thermal capture rate constants are derived from the model for the temperature range between 0 and 10 K relevant for astrochemistry. Comparison of the calculated thermal capture rate coefficients with the absolute reaction rates measured above 27 K by Marquette et al. (Chem. Phys. Lett., 1985, 122, 431) suggests that only 40% of the close collisions are reactive.
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18
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Clausen G, Jansen P, Scheidegger S, Agner JA, Schmutz H, Merkt F. Ionization Energy of the Metastable 2 ^{1}S_{0} State of ^{4}He from Rydberg-Series Extrapolation. Phys Rev Lett 2021; 127:093001. [PMID: 34506206 DOI: 10.1103/physrevlett.127.093001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
In a recent breakthrough in first-principles calculations of two-electron systems, Patkóś, Yerokhin, and Pachucki [Phys. Rev. A 103, 042809 (2021)PLRAAN2469-992610.1103/PhysRevA.103.042809] have performed the first complete calculation of the Lamb shift of the helium 2 ^{3}S_{1} and 2 ^{3}P_{J} triplet states up to the term in α^{7}m. Whereas their theoretical result of the frequency of the 2 ^{3}P←2 ^{3}S transition perfectly agrees with the experimental value, a more than 10σ discrepancy was identified for the 3 ^{3}D←2 ^{3}S and 3 ^{3}D←2 ^{3}P transitions, which hinders the determination of the He^{2+} charge radius from atomic spectroscopy. We present here a new measurement of the ionization energy of the 2 ^{1}S_{0} state of He [960 332 040.491(32) MHz] which we use in combination with the 2 ^{3}S_{1}←2 ^{1}S_{0} interval measured by Rengelink et al. [Nat. Phys. 14, 1132 (2018).NPAHAX1745-247310.1038/s41567-018-0242-5] and the 2 ^{3}P←2 ^{3}S_{1} interval measured by Zheng et al. [Phys. Rev. Lett. 119, 263002 (2017)PRLTAO0031-900710.1103/PhysRevLett.119.263002] and Cancio Pastor et al. [Phys. Rev. Lett. 92, 023001 (2004)PRLTAO0031-900710.1103/PhysRevLett.92.023001] to derive experimental ionization energies of the 2 ^{3}S_{1} state [1152 842 742.640(32) MHz] and the 2 ^{3}P centroid energy [876 106 247.025(39) MHz]. These values reveal disagreements with the α^{7}m Lamb shift prediction by 6.5σ and 10σ, respectively, and support the suggestion by Patkóš et al. of an unknown theoretical contribution to the Lamb shifts of the 2 ^{3}S and 2 ^{3}P states of He.
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Affiliation(s)
- Gloria Clausen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Simon Scheidegger
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Josef A Agner
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hansjürg Schmutz
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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19
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Wehrli D, Génévriez M, Knecht S, Reiher M, Merkt F. Charge-Transfer-Induced Predissociation in Rydberg States of Molecular Cations: MgAr . J Phys Chem A 2021; 125:6681-6696. [PMID: 34319723 PMCID: PMC8775275 DOI: 10.1021/acs.jpca.1c03859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/11/2021] [Indexed: 11/28/2022]
Abstract
Very little is known about the Rydberg states of molecular cations, i.e., Rydberg states having a doubly charged ion core. With the example of MgAr+, we present general features of the structure and dynamics of the Rydberg states of molecular cations, which we find are subject to the process of charge-transfer-induced predissociation. Our study focuses on the spectrum of low-n Rydberg states with potential-energy functions associated with the Mg+(3d and 4s) + Ar(1S0) dissociation asymptotes. In particular, we have recorded spectra of the 3dπΩ' (Ω' = 1/2, 3/2) Rydberg states, extending from the lowest (v' = 0) vibrational levels to their dissociation limits. This spectral range encompasses the region where the onset of predissociation by interaction with the mostly repulsive 2Σ and 2Π charge-transfer states associated with the Mg(3s2) + Ar+(2P1/2,3/2) dissociation asymptotes is observed. This interaction leads to very strong perturbations of the 3dπ Rydberg states of MgAr+, revealed by vibrational progressions exhibiting large and rapid variations of the vibrational intervals, line widths, and spin-orbit splittings. We attribute the anomalous sign and magnitude of the spin-orbit coupling constant of the 3dπ state to the interaction with a 2Π Rydberg state correlating to the Mg+(4p) + Ar(1S0) dissociation limit. To analyze our spectra and elucidate the underlying process of charge-transfer-induced predissociation, we implemented a model that allowed us to derive the potential-energy functions of the charge-transfer states and to quantitatively reproduce the experimental results. This analysis characterizes the main features of the dynamics of the Rydberg series converging to the ground state of MgAr2+. We expect that the results and analysis reported here are qualitatively valid for a broader range of singly charged molecular cations, which are inherently prone to charge-transfer interactions.
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Affiliation(s)
- Dominik Wehrli
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Matthieu Génévriez
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Stefan Knecht
- Abteilung
SHE Chemie, GSI Helmholtzzentrum für
Schwerionenforschung, DE-64291 Darmstadt, Germany
| | - Markus Reiher
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
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20
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Husmann D, Bernier LG, Bertrand M, Calonico D, Chaloulos K, Clausen G, Clivati C, Faist J, Heiri E, Hollenstein U, Johnson A, Mauchle F, Meir Z, Merkt F, Mura A, Scalari G, Scheidegger S, Schmutz H, Sinhal M, Willitsch S, Morel J. SI-traceable frequency dissemination at 1572.06 nm in a stabilized fiber network with ring topology. Opt Express 2021; 29:24592-24605. [PMID: 34614812 DOI: 10.1364/oe.427921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/03/2021] [Indexed: 06/13/2023]
Abstract
Frequency dissemination in phase-stabilized optical fiber networks for metrological frequency comparisons and precision measurements are promising candidates to overcome the limitations imposed by satellite techniques. However, in an architecture shared with telecommunication data traffic, network constraints restrict the availability of dedicated channels in the commonly-used C-band. Here, we demonstrate the dissemination of an SI-traceable ultrastable optical frequency in the L-band over a 456 km fiber network with ring topology, in which data traffic occupies the full C-band. We characterize the optical phase noise and evaluate a link instability of 4.7 × 10-16 at 1 s and 3.8 × 10-19 at 2000 s integration time, and a link accuracy of 2 × 10-18. We demonstrate the application of the disseminated frequency by establishing the SI-traceability of a laser in a remote laboratory. Finally, we show that our metrological frequency does not interfere with data traffic in the telecommunication channels. Our approach combines an unconventional spectral choice in the telecommunication L-band with established frequency-stabilization techniques, providing a novel, cost-effective solution for ultrastable frequency-comparison and dissemination, and may contribute to a foundation of a world-wide metrological network.
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21
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Höveler K, Deiglmayr J, Merkt F. Deviation of the rate of the reaction from Langevin behaviour below 1 K, branching ratios for the and product channels, and product-kinetic-energy distributions. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1954708] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Johannes Deiglmayr
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
- Department of Physics, University of Leipzig, Leipzig, Germany
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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Wehrli D, Génévriez M, Merkt F. Spectroscopic characterization of a thermodynamically stable doubly charged diatomic molecule: MgAr 2. Phys Chem Chem Phys 2021; 23:10978-10987. [PMID: 33928972 PMCID: PMC8115400 DOI: 10.1039/d1cp00730k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Although numerous doubly positively charged diatomic molecules (diatomic dications) are known from investigations using mass spectrometry and ab initio quantum chemistry, only three of them, NO2+, N22+ and DCl2+, have been studied using rotationally resolved optical spectroscopy and only about a dozen by vibrationally resolved double-ionization methods. So far, no thermodynamically stable diatomic dication has been characterized spectroscopically, primarily because of experimental difficulties associated with their synthesis in sufficient densities in the gas phase. Indeed, such molecules typically involve, as constituents, rare-gas, halogen, chalcogen, and metal atoms. We report here on a new approach to characterize molecular dications based on high-resolution photoelectron spectroscopy of the singly charged parent molecular cation and present the first spectroscopic characterization of a thermodynamically stable diatomic dication, MgAr2+. From the fully resolved vibrational and partially resolved rotational structures of the photoelectron spectra of 24MgAr+ and 26MgAr+, we determined the potential-energy function of the electronic ground state of MgAr2+, its dissociation (binding) energy (D0 = 10 690(3) cm−1), and its harmonic (ωe(24MgAr2+) = 327.02(11) cm−1) and anharmonic (ωexe(24MgAr2+) = 2.477(15) cm−1) vibrational constants. The analysis enables us to explain quantitatively how the strong bond arises in this dication despite the fact that Ar and Mg2+ both have a full-shell rare-gas electronic configuration. We present a new method to study doubly charged molecules relying on high-resolution spectroscopy of the singly charged parent cation, and report on the first spectroscopic characterization of a thermodynamically stable diatomic dication, MgAr2+.![]()
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Affiliation(s)
- Dominik Wehrli
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
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23
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Wörner HJ, Merkt F. Corrigendum: Jahn-Teller Effects in Molecular Cations Studied by Photoelectron Spectroscopy and Group Theory. Angew Chem Int Ed Engl 2021; 60:8009. [PMID: 33784441 DOI: 10.1002/anie.202016700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Wörner H, Merkt F. Berichtigung: Untersuchung des Jahn‐Teller‐Effekts in molekularen Kationen mithilfe von Photoelektronenspektroskopie und Gruppentheorie. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202016700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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25
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Affiliation(s)
- D. Wehrli
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - U. Hollenstein
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - F. Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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26
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Wörner HJ, Qian X, Merkt F. Erratum: "Jahn-Teller effect in tetrahedral symmetry: Large-amplitude tunneling motion and rovibronic structure of CH 4 + and CD 4 +" [J. Chem. Phys. 126, 144305 (2007)]. J Chem Phys 2021; 154:069901. [PMID: 33588541 DOI: 10.1063/5.0029342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- H J Wörner
- Labaoratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
| | - X Qian
- Labaoratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
| | - F Merkt
- Labaoratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
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27
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Grütter M, Wörner HJ, Merkt F. Erratum: "Rovibronic analysis of the Jahn-Teller effect in CH 2D 2 + at low energies" [J. Chem. Phys. 131, 024309 (2009)]. J Chem Phys 2021; 154:069902. [PMID: 33588530 DOI: 10.1063/5.0040240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M Grütter
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093, Zurich, Switzerland
| | - H J Wörner
- NRC Steacie Institute for Molecular Sciences, Ottawa, Ontario K1A 0R6, Canada
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093, Zurich, Switzerland
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28
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Höveler K, Deiglmayr J, Agner JA, Schmutz H, Merkt F. The H 2+ + HD reaction at low collision energies: H 3+/H 2D + branching ratio and product-kinetic-energy distributions. Phys Chem Chem Phys 2021; 23:2676-2685. [PMID: 33480928 DOI: 10.1039/d0cp06107g] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fully state-selected reactions between H2+ molecules in the X+ 2Σg+(v+ = 0, N+ = 0) state and HD molecules in the X 1Σg+(v = 0, J = 0) state forming H3+ + D and H2D+ + H have been studied at collision energies Ecoll between 0 and kB·30 K with a resolution of about 75 mK at the lowest energies. H2 molecules in a supersonic beam were prepared in Rydberg-Stark states with principal quantum number n = 27 and merged with a supersonic beam of ground-state HD molecules using a curved surface-electrode Rydberg-Stark decelerator and deflector. The reaction between H2+ and HD was studied within the orbit of the Rydberg electron to avoid heating of the ions by stray electric fields. The reaction was observed for well-defined and adjustable time intervals, called reaction-observation windows, between two electric-field pulses. The first pulse swept all ions away from the reaction volume and its falling edge defined the beginning of the reaction-observation window. The second pulse extracted the product ions toward a charged-particle detector located at the end of a time-of-flight tube and its rising edge defined the end of the reaction-observation window. Monitoring and analysing the time-of-flight distributions of the H3+ and H2D+ products in dependence of the duration of the reaction-observation window enabled us to obtain information on the kinetic-energy distribution of the product ions and determine branching ratios of the H3+ + D and H2D+ + H reaction channels. The mean product-kinetic-energy release is 0.46(5) eV, representing 27(3)% of the available energy, and the H3+ + D product branching ratio is 0.225(20). The relative reaction rates correspond closely to Langevin capture rates down to the lowest energies probed experimentally (≈kB·50 mK).
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Affiliation(s)
- Katharina Höveler
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Johannes Deiglmayr
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Josef A Agner
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Hansjürg Schmutz
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
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29
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Wörner HJ, Merkt F. Erratum: "Jahn-Teller effect in CH 3D + and CD 3H +: Conformational isomerism, tunneling-rotation structure, and the location of conical intersections" [J. Chem. Phys. 126, 154304 (2007)]. J Chem Phys 2021; 154:049901. [PMID: 33514118 DOI: 10.1063/5.0029341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- H J Wörner
- Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
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30
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Zhelyazkova V, Martins FBV, Agner JA, Schmutz H, Merkt F. Ion-Molecule Reactions below 1 K: Strong Enhancement of the Reaction Rate of the Ion-Dipole Reaction He^{+}+CH_{3}F. Phys Rev Lett 2020; 125:263401. [PMID: 33449728 DOI: 10.1103/physrevlett.125.263401] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 10/14/2020] [Accepted: 11/04/2020] [Indexed: 06/12/2023]
Abstract
The reaction between He^{+} and CH_{3}F forming predominantly CH_{2}^{+} and CHF^{+} has been studied at collision energies E_{coll} between 0 and k_{B}·10 K in a merged-beam apparatus. To avoid heating of the ions by stray electric fields, the reaction was observed within the orbit of a highly excited Rydberg electron. Supersonic beams of CH_{3}F and He(n) Rydberg atoms with principal quantum number n=30 and 35 were merged and their relative velocity tuned using a Rydberg-Stark decelerator and deflector, allowing an energy resolution of 150 mK. A strong enhancement of the reaction rate was observed below E_{coll}/k_{B}=1 K. The experimental results are interpreted with an adiabatic capture model that accounts for the state-dependent orientation of the polar CH_{3}F molecules by the Stark effect as they approach the He^{+} ion. The enhancement of the reaction rate at low collision energies is primarily attributed to para-CH_{3}F molecules in the J=1, KM=1 high-field-seeking states, which represent about 8% of the population at the 6 K rotational temperature of the supersonic beam.
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Affiliation(s)
| | | | - Josef A Agner
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hansjürg Schmutz
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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31
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Jansen P, Merkt F. Manipulating beams of paramagnetic atoms and molecules using inhomogeneous magnetic fields. Prog Nucl Magn Reson Spectrosc 2020; 120-121:118-148. [PMID: 33198967 DOI: 10.1016/j.pnmrs.2020.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/07/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
We review methods to manipulate the motion of pulsed supersonic atomic and molecular beams using time-independent and -dependent inhomogeneous magnetic fields. In addition, we discuss current and possible future applications and research directions.
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Affiliation(s)
- Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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32
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Wehrli D, Génévriez M, Knecht S, Reiher M, Merkt F. Complete characterization of the 3p Rydberg complex of a molecular ion: MgAr+. I. Observation of the Mg(3pσ)Ar+ B+ state and determination of its structure and dynamics. J Chem Phys 2020; 153:074310. [DOI: 10.1063/5.0015603] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Dominik Wehrli
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Matthieu Génévriez
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Stefan Knecht
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Markus Reiher
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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33
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Génévriez M, Wehrli D, Merkt F. Complete characterization of the 3p Rydberg complex of a molecular ion: MgAr+. II. Global analysis of the A+ 2Π and B+ 2Σ+ (3pσ,π) states. J Chem Phys 2020; 153:074311. [DOI: 10.1063/5.0015608] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Matthieu Génévriez
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Dominik Wehrli
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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34
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Willitsch S, Boudon V, De Natale P, Huet T, Merkt F. Editorial. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1759289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Stefan Willitsch
- Department of Chemistry, Universtiy of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
- Editors of Molecular Physics
| | - Vincent Boudon
- Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS – Université de Bourgogne, Dijon, France
- Chairman of the 26th HRMS Conference
| | - Paolo De Natale
- Istituto Nazionale di Ottica – CNR & European Laboratory for Nonlinear Spectroscopy LENS, Florence, Italy
- Member of the HRMS Executive Committee
| | - Thérèse Huet
- Member of the HRMS Executive Committee
- Université Lille, CNRS, F-59000 Lille, France
| | - Frédéric Merkt
- Member of the HRMS Executive Committee
- Laboratorium für Physikalische Chemie ETH Zürich, 8093 Zürich, Switzerland
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35
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Semeria L, Jansen P, Camenisch GM, Mellini F, Schmutz H, Merkt F. Precision Measurements in Few-Electron Molecules: The Ionization Energy of Metastable ^{4}He_{2} and the First Rotational Interval of ^{4}He_{2}^{+}. Phys Rev Lett 2020; 124:213001. [PMID: 32530687 DOI: 10.1103/physrevlett.124.213001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
Molecular helium represents a benchmark system for testing ab initio calculations on few-electron molecules. We report on the determination of the adiabatic ionization energy of the a ^{3}Σ_{u}^{+} state of He_{2}, corresponding to the energy interval between the a ^{3}Σ_{u}^{+} (v^{''}=0, N^{''}=1) state of He_{2} and the X^{+} ^{2}Σ_{u}^{+} (v^{+}=0, N^{+}=1) state of He_{2}^{+}, and of the lowest rotational interval of He_{2}^{+}. These measurements rely on the excitation of metastable He_{2} molecules to high Rydberg states using frequency-comb-calibrated continuous-wave UV radiation in a counterpropagating laser-beam setup. The observed Rydberg states were extrapolated to their series limit using multichannel quantum-defect theory. The ionization energy of He_{2} (a ^{3}Σ_{u}^{+}) and the lowest rotational interval of He_{2}^{+} (X^{+} ^{2}Σ_{u}^{+}) are 34 301.207 002(23)±0.000 037_{syst} cm^{-1} and 70.937 589(23)±0.000 060_{syst} cm^{-1}, respectively.
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Affiliation(s)
- Luca Semeria
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Federico Mellini
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hansjürg Schmutz
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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36
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Abstract
In this contribution, we describe the status of the development of a precision-spectroscopic experiment aimed at measuring transitions to states of high principal quantum number n of the hydrogen atom (H). These states form series (called Rydberg series) which converge for n → ∞ to the ionization threshold of H. The ionization energy of H can thus be determined directly by measuring the frequencies of transitions to high-n states and extrapolating the Rydberg series to n → ∞.
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Affiliation(s)
- Simon Scheidegger
- ETH Zurich, Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland;,
| | - Frédéric Merkt
- ETH Zurich, Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland;,
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37
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Affiliation(s)
- M. Génévriez
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - D. Wehrli
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - F. Merkt
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
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38
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Wehrli D, Génévriez M, Kreis C, Agner JA, Merkt F. Determination of the Interaction Potential and Rovibrational Structure of the Ground Electronic State of MgAr+ Using PFI-ZEKE Photoelectron Spectroscopy. J Phys Chem A 2019; 124:379-385. [DOI: 10.1021/acs.jpca.9b10435] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dominik Wehrli
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Matthieu Génévriez
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Carla Kreis
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Josef A. Agner
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
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39
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Garcia S, Stammeier M, Deiglmayr J, Merkt F, Wallraff A. Single-Shot Nondestructive Detection of Rydberg-Atom Ensembles by Transmission Measurement of a Microwave Cavity. Phys Rev Lett 2019; 123:193201. [PMID: 31765186 DOI: 10.1103/physrevlett.123.193201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Indexed: 06/10/2023]
Abstract
We present an experimental realization of single-shot nondestructive detection of ensembles of helium Rydberg atoms. We use the dispersive frequency shift of a superconducting microwave cavity interacting with the ensemble. By probing the transmission of the cavity, we determine the number of Rydberg atoms or the populations of Rydberg quantum states when the ensemble is prepared in a superposition. At the optimal microwave probe power, determined by the critical photon number, we reach single-shot detection of the atom number with 13% relative precision for ensembles of about 500 Rydberg atoms with a measurement backaction characterized by approximately 2% population transfer.
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Affiliation(s)
- S Garcia
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - M Stammeier
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J Deiglmayr
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
| | - A Wallraff
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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40
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Merkt F, Fielding HH, Mackenzie SR. A personal preface to the special issue of Molecular Physics in Honour of Professor Timothy P. Softley, FRS. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1619307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Stuart R. Mackenzie
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
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41
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Hollenstein U, Dulitz K, Merkt F. The adiabatic ionisation energy of CO 2. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1600061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- U. Hollenstein
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - K. Dulitz
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
- Present address: Nanophysics Research Group, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany
| | - F. Merkt
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
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42
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Beyer M, Hölsch N, Hussels J, Cheng CF, Salumbides EJ, Eikema KSE, Ubachs W, Jungen C, Merkt F. Determination of the Interval between the Ground States of Para- and Ortho-H_{2}. Phys Rev Lett 2019; 123:163002. [PMID: 31702363 DOI: 10.1103/physrevlett.123.163002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Indexed: 06/10/2023]
Abstract
Nuclear-spin-symmetry conservation makes the observation of transitions between quantum states of ortho- and para-H_{2} extremely challenging. Consequently, the energy-level structure of H_{2} derived from experiment consists of two disjoint sets of level energies, one for para-H_{2} and the other for ortho-H_{2}. We use a new measurement of the ionization energy of para-H_{2} [E_{I}(H_{2})/(hc)=124 417.491 098(31) cm^{-1}] to determine the energy separation [118.486 770(50) cm^{-1}] between the ground states of para- and ortho-H_{2} and thus link the energy-level structure of the two nuclear-spin isomers of this fundamental molecule. Comparison with recent theoretical results [M. Puchalski et al., Phys. Rev. Lett. 122, 103003 (2019)PRLTAO0031-900710.1103/PhysRevLett.122.103003] enables the derivation of an upper bound of 1.5 MHz for a hypothetical global shift of the energy-level structure of ortho-H_{2} with respect to that of para-H_{2}.
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Affiliation(s)
- M Beyer
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
| | - N Hölsch
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
| | - J Hussels
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
| | - C-F Cheng
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
| | - E J Salumbides
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
| | - K S E Eikema
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
| | - W Ubachs
- Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
| | - Ch Jungen
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
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43
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Herburger H, Hollenstein U, Agner JA, Merkt F. PFI-ZEKE-photoelectron spectroscopy of N 2O using narrow-band VUV laser radiation generated by four-wave mixing in Ar using a KBBF crystal. J Chem Phys 2019; 151:144302. [PMID: 31615237 DOI: 10.1063/1.5124477] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A new nonlinear optical scheme relying on sum-frequency mixing in a KBe2BO3F2 crystal has been used to generate intense, broadly tunable, narrow-bandwidth, coherent vacuum-ultraviolet (VUV) radiation beyond 16 eV by resonance-enhanced four-wave mixing in Ar. The VUV radiation was used to record high-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the N2O+ A+ ← N2O X photoionizing transition in the wave-number range from 132 000 cm-1 to 135 000 cm-1. The rotational structure of almost all vibrational levels of the A+ state with vibrational term values up to 2700 cm-1 could be resolved, and improved values of the first two adiabatic ionization energies of N2O, corresponding to the formation of the X+ 2Π3/2(000) J+ = 3/2 and A+ 2Σ+(000) N+ = 0 levels of N2O+ from the X 1Σ+(000) J″ = 0 ground state [103 969.30(12) cm-1 and 132 197.70(12) cm-1, respectively], were derived. The rotational intensity distributions of the bands were found to depend strongly on the value of the vibrational angular momentum of the ionic levels. The vibrational structure is discussed in terms of previously reported effective-Hamiltonian analyses.
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Affiliation(s)
- H Herburger
- Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - U Hollenstein
- Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - J A Agner
- Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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44
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Affiliation(s)
- V. Zhelyazkova
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - M. Žeško*
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - H. Schmutz
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - J. A. Agner
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - F. Merkt
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
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45
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Hölsch N, Beyer M, Salumbides EJ, Eikema KSE, Ubachs W, Jungen C, Merkt F. Benchmarking Theory with an Improved Measurement of the Ionization and Dissociation Energies of H_{2}. Phys Rev Lett 2019; 122:103002. [PMID: 30932670 DOI: 10.1103/physrevlett.122.103002] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/29/2019] [Indexed: 06/09/2023]
Abstract
The dissociation energy of H_{2} represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF ^{1}Σ_{g}^{+}(v=0,N=1) state and the 54p1_{1} Rydberg state of H_{2}. When combined with previously determined intervals, this new measurement leads to an improved value of the dissociation energy D_{0}^{N=1} of ortho-H_{2} that has, for the first time, reached a level of uncertainty that is 3 times smaller than the contribution of about 1 MHz resulting from the finite size of the proton. The new result of 35 999.582 834(11) cm^{-1} is in remarkable agreement with the theoretical result of 35 999.582 820(26) cm^{-1} obtained in calculations including high-order relativistic and quantum-electrodynamics corrections, as reported in the following Letter [M. Puchalski, J. Komasa, P. Czachorowski, and K. Pachucki, Phys. Rev. Lett. 122, 103003 (2019)PRLTAO0031-900710.1103/PhysRevLett.122.103003]. This agreement resolves a recent discrepancy between experiment and theory that had hindered a possible use of the dissociation energy of H_{2} in the context of the current controversy on the charge radius of the proton.
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Affiliation(s)
- Nicolas Hölsch
- Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
| | - Maximilian Beyer
- Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
| | - Edcel J Salumbides
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Kjeld S E Eikema
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Wim Ubachs
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Christian Jungen
- Department of Physics and Astronomy, University College London, London, WC1E 6BT United Kingdom
| | - Frédéric Merkt
- Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland
- LaserLaB, Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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46
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Affiliation(s)
- C. Lauzin
- Institute of condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - H. Schmutz
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - J. A. Agner
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
| | - F. Merkt
- Physical Chemistry Laboratory, ETH Zürich, Zürich, Switzerland
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47
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Jacovella U, Merkt F. High-resolution photoelectron spectrum of the origin band of the X̃ + 2E ← X̃ 1A 1 ionising transition of propyne. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1451002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- U. Jacovella
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich , Zurich, Switzerland
| | - F. Merkt
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich , Zurich, Switzerland
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48
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Beyer M, Merkt F. Hyperfine-interaction-induced g/u mixing and its implication on the existence of the first excited vibrational level of the A + Σ u + 2 state of H 2 + and on the scattering length of the H + H + collision. J Chem Phys 2018; 149:214301. [PMID: 30525720 DOI: 10.1063/1.5046147] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Ab initio calculations of the energy level structure of H 2 + that include relativistic and radiative corrections to nonrelativistic energies and the diagonal part of the hyperfine interaction have predicted the existence of four bound rovibrational levels [(v = 0, N = 0 - 2) and (v = 1, N = 0)] of the first electronically excited ( A + Σ u + 2 ) state of H 2 + , the (v = 1, N = 0) level having a calculated binding energy of only E b = 1.082 219 8(4)·10-9 Eh and leading to an extremely large scattering length of 750(5) a0 for the H+ + H collision [J. Carbonell et al., J. Phys. B: At., Mol. Opt. Phys. 37, 2997 (2004)]. We present an investigation of the nonadiabatic coupling between the first two electronic states ( X + Σ g + 2 and A + Σ u + 2 ) of H 2 + induced by the Fermi-contact term of the hyperfine-coupling Hamiltonian. This interaction term, which mixes states of total spin quantum number G = 1/2, is rigorously implemented in a close-coupling approach to solve the spin-rovibronic Schrödinger equation. We show that it mixes states of gerade and ungerade electronic symmetry, that it shifts the positions of all weakly bound rovibrational states of H 2 + , and that it affects both the positions and widths of its shape resonances. The calculations demonstrate that the G = 1/2 hyperfine component of the A+ (v = 1, N = 0) state does not exist and that, for G = 1/2, the s-wave scattering lengths of the H+ + H(1s) collision are -578(6) a0 and -43(4) a0 for the F = 0 and F = 1 hyperfine components of the H(1s) atom, respectively. The binding energy of the G = 3/2 hyperfine component of the A+ (v = 1, N = 0) state is not significantly affected by the hyperfine interaction and the corresponding scattering length for the H+ + H(1s, F = 1) collision is 757(7) a0.
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Affiliation(s)
- Maximilian Beyer
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
| | - Frédéric Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
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49
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Hölsch N, Beyer M, Merkt F. Nonadiabatic effects on the positions and lifetimes of the low-lying rovibrational levels of the GK 1Σ and H 1Σ states of H 2. Phys Chem Chem Phys 2018; 20:26837-26845. [PMID: 30328429 DOI: 10.1039/c8cp05233f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The term values of rovibrational levels of the GK 1Σ+g and H 1Σ+g states of H2 have been measured with absolute and relative accuracies down to 10-4 cm-1 (≈3 MHz) and 10-6 cm-1 (≈30 kHz), respectively, by measuring transitions to long-lived high-n Rydberg states using single-mode cw laser radiation and a collimated supersonic beam of cold H2 molecules. The term values are compared with those determined in earlier experimental and theoretical investigations and the comparison points at discrepancies and a need for improved theoretical treatments of nonadiabatic, relativistic and radiative corrections for these states. The lifetimes of several low-lying rovibrational levels of the GK, H and I+ 1Πg states have been determined in pump-probe experiments. These lifetimes reveal a significant dependence on the electronic, vibrational and rotational excitation and also deviate from results obtained in earlier experimental and theoretical investigations.
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Affiliation(s)
- Nicolas Hölsch
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
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50
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Jansen P, Semeria L, Merkt F. Fundamental vibration frequency and rotational structure of the first excited vibrational level of the molecular helium ion ( He 2 + ). J Chem Phys 2018; 149:154302. [PMID: 30342452 DOI: 10.1063/1.5051089] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The term values of the rotational levels of the first excited vibrational state of the electronic ground state of He 2 + with a rotational quantum number N + ≤ 13 have been determined with an accuracy of 1.2 × 10-3 cm-1 (∼35 MHz) by multichannel-quantum-defect-theory-assisted Rydberg spectroscopy of metastable He2. Comparison of the experimental term values with the most accurate ab initio results for He 2 + available in the literature [W.-C. Tung, M. Pavanello, and L. Adamowicz, J. Chem. Phys. 136, 104309 (2012)] reveals inconsistencies between the theoretical and experimental results that increase with increasing rotational quantum numbers. The fundamental vibrational wavenumber of He 2 + was determined to be 1628.3832(12) cm-1 by fitting effective molecular constants to the obtained term values.
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Affiliation(s)
- Paul Jansen
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Luca Semeria
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Frédéric Merkt
- Laboratory of Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland
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