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del Mazo-Sevillano P, Félix-González D, Aguado A, Sanz-Sanz C, Kwon DH, Roncero O. Vibrational, non-adiabatic and isotopic effects in the dynamics of the H 2 + H 2+ → H 3+ + H reaction: application to plasma modelling. Mol Phys 2023. [DOI: 10.1080/00268976.2023.2183071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Affiliation(s)
- P. del Mazo-Sevillano
- Department of Mathematics and Computer Science, FU Berlin, Berlin, Germany
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, Madrid, Spain
| | - D. Félix-González
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, Madrid, Spain
| | - A. Aguado
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, Madrid, Spain
| | - C. Sanz-Sanz
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, Madrid, Spain
| | - D.-H. Kwon
- Nuclear Physics Application Research Division, Korea Atomic Energy Research Institute, Daejeon, Republic of Korea
| | - O. Roncero
- Instituto de Física Fundamental, IFF-CSIC, Madrid, Spain
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2
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Braunstein M, Bonnet L, Roncero O. Capturing quantum effects with quasi-classical trajectories in the D + H+3 → H 2D + + H reaction. Phys Chem Chem Phys 2022; 24:5489-5505. [PMID: 35171152 DOI: 10.1039/d1cp04244k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present quasi-classical trajectory (QCT) cross sections, rate constants, and product state distributions for the D + H+3 → H2D+ + H reaction. Using the same H+4 potential surface, the rate constants obtained from several QCT-based methods correcting for zero-point effects by Gaussian binning the product H2D+ are compared to ring polymer molecular dynamics (RPMD) rate constants [Bulut et al., J. Phys. Chem. A, 2019, 123, 8766] which include quantum effects and to recent experimentally derived rate constants [Bowen et al., J. Chem. Phys., 2021, 154, 084307]. QCT with standard binning predicts rate constants that increase slowly as the temperature decreases from 1500 to 100 K. In contrast, the RPMD rate constants decrease rapidly with decreasing temperature. By 100 K, the QCT standard binning rate constant is more than 3 orders of magnitude larger than the RPMD rate constant. We show that QCT with Gaussian binning and proper normalization captures the zero-point effects and reproduces the RPMD rate constants over a large temperature range. Furthermore, the simple technique of counting only reactive trajectories with vibrational energy above the product zero-point energy matches the RPMD results well down to ∼300 K. The present Gaussian binned rate constants are in fair agreement with new experimentally derived rate constants from 100 to 1500 K. However, because the Gaussian binned rate constants do not include tunneling, important at lower temperatures, and the RPMD and experimentally derived rate constants have significant differences, the roles of the competing effects of zero-point energy, internal excitation of the H+3, and quantum tunneling are not simple and require further study for a consistent picture of the dynamics. Since rate constants for complex forming reactions, such as the title reaction, are difficult to converge with RPMD, alternative QCT-based methods, which include quantum effects and in addition provide product state distributions as described here, are highly desirable.
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Affiliation(s)
- Matthew Braunstein
- Spectral Sciences Incorporated, 4 Fourth Avenue, Burlington, MA 01824, USA.
| | - Laurent Bonnet
- CNRS, Université de Bordeaux, ISM, UMR 5255, F-33400 Talence, France
| | - Octavio Roncero
- Instituto de Fisica Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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3
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Bulut N, Aguado A, Sanz-Sanz C, Roncero O. Quantum Effects on the D + H 3+ → H 2D + + H Deuteration Reaction and Isotopic Variants. J Phys Chem A 2019; 123:8766-8775. [PMID: 31545608 DOI: 10.1021/acs.jpca.9b06081] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The title reaction and its isotopic variants are studied using quasi-classical trajectory (QCT) (without taking into account corrections to account for the possible zero point energy breakdown) and ring polymer molecular dynamics (RPMD) methods with a full dimensional and accurate potential energy surface which presents an exchange barrier of approximately 0.144 eV. The QCT rate constant increases when the temperature decreases from 1500 to 10 K. On the contrary, the RPMD rate constant decreases with decreasing temperature, in semiquantitative agreement with recent experimental results. The present RPMD results are in between the thermal and translational experimental rate constants, extracted from the measured data to eliminate the initial vibrational excitation of H3+, obtained in an arc discharge. The difference between the present RPMD results and experimental values is attributed to the possible existence of non thermal vibrational excitation of H3+, not completely removed by the semiempirical model used for the analysis of the experimental results. Also, it is found that, below 200 K, the RPMD trajectories are trapped, forming long-lived collision complexes, with lifetimes longer than 1 ns. These collision complexes can fragment by either redissociating back to reactants or react to products, in the two cases tunneling through the centrifugal and reaction barriers, respectively. The contribution of the formation of the complex to the total deuteration rate should be calculated with more accurate quantum methods, as has been found recently for reactions of larger systems, and the present four atoms system is a good candidate to benchmark the adequacy of RPMD method at temperatures below 100 K.
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Affiliation(s)
- Niyazi Bulut
- Department of Physics , Firat University , 23169 Elazig , Turkey
| | - Alfredo Aguado
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias, Módulo 14 , Universidad Autónoma de Madrid , 28049 , Madrid , Spain
| | - Cristina Sanz-Sanz
- Unidad Asociada UAM-IFF-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias, Módulo 14 , Universidad Autónoma de Madrid , 28049 , Madrid , Spain
| | - Octavio Roncero
- Instituto de Física Fundamental (IFF-CSIC), C.S.I.C. , Serrano 123 , 28006 Madrid , Spain
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4
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Dohnal P, Shapko D, Kálosi Á, Kassayová M, Roučka Š, Rednyk S, Plašil R, Hejduk M, Glosík J. Towards state selective recombination of H 3+ under astrophysically relevant conditions. Faraday Discuss 2019; 217:220-234. [PMID: 31016318 DOI: 10.1039/c8fd00214b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present studies on the thermalisation of H3+ ions in a cold He/Ar/H2 plasma at temperatures 30-70 K. We show that we are able to generate a rotationally thermalised H3+ ensemble with a population of rotational and nuclear spin states corresponding to a particular ion translational temperature. By varying the para-H2 fraction used in the experiment we are able to produce para-H3+ ions with fractional populations higher than those corresponding to thermodynamic values. At 35 K, only the lowest rotational states of para and ortho H3+ are populated. This is the first step towards experimental studies of electron-molecular ion recombination processes with precisely specified quantum states at astrophysically relevant temperatures.
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Affiliation(s)
- Petr Dohnal
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Dmytro Shapko
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Ábel Kálosi
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Miroslava Kassayová
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Štěpán Roučka
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Serhiy Rednyk
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Radek Plašil
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
| | - Michal Hejduk
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, UK
| | - Juraj Glosík
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Praha 8-Libeň, Czech Republic.
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5
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Suleimanov YV, Aguado A, Gómez-Carrasco S, Roncero O. A Ring Polymer Molecular Dynamics Approach to Study the Transition between Statistical and Direct Mechanisms in the H 2 + H 3+ → H 3+ + H 2 Reaction. J Phys Chem Lett 2018; 9:2133-2137. [PMID: 29633841 PMCID: PMC6031303 DOI: 10.1021/acs.jpclett.8b00783] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Because of its fundamental importance in astrochemistry, the H2 + H3+ → H3+ + H2 reaction has been studied experimentally in a wide temperature range. Theoretical studies of the title reaction significantly lag primarily because of the challenges associated with the proper treatment of the zero-point energy (ZPE). As a result, all previous theoretical estimates for the ratio between a direct proton-hop and indirect exchange (via the H5+ complex) channels deviate from the experiment, in particular, at lower temperatures where the quantum effects dominate. In this work, the ring polymer molecular dynamics (RPMD) method is applied to study this reaction, providing very good agreement with the experiment. RPMD is immune to the shortcomings associated with the ZPE leakage and is able to describe the transition from direct to indirect mechanisms below room temperature. We argue that RPMD represents a useful tool for further studies of numerous ZPE-sensitive chemical reactions that are of high interest in astrochemistry.
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Affiliation(s)
- Yury V. Suleimanov
- Computation-based Science and Technology Research Center, Cyprus Institute, 20 Kavafi Str., Nicosia 2121, Cyprus
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States
| | - Alfredo Aguado
- Unidad Asociada UAM-CSIC, Departamento de Química Física Aplicada, Facultad de Ciencias M-14, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | | | - Octavio Roncero
- Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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6
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Lin Z, McCoy AB. Probing the Relationship Between Large-Amplitude Motions in H5(+) and Proton Exchange Between H3(+) and H2. J Phys Chem A 2015; 119:12109-18. [PMID: 26244451 DOI: 10.1021/acs.jpca.5b05774] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the spectroscopy and dynamics of H5(+) is central in gaining insights into the H3(+) + H2 → H5(+) → H2 + H3(+) proton transfer reaction. This molecular ion exhibits large-amplitude vibrations, which allow for the transfer of a proton between H3(+) and H2 even in its ground vibrational state. With vibrational excitation, the number of open channels for permutations of protons increase. In this work, the minimized energy path variant of diffusion Monte Carlo is used to investigate how the energetically accessible proton permutations evolve as H5(+) is dissociated into H3(+) + H2. Two mechanisms for proton permutation are investigated. The first is the proton hop, which correlates to large-amplitude vibrations of the central proton in H5(+). The second is the exchange of a pair of hydrogen atoms between H3(+) and H2. This mechanism requires several proton hops along with a 120° rotation of H3(+) within the H5(+) molecular ion. This analysis shows that while there is a narrow region of configuration space over which both isomerization processes are energetically accessible, full permutation of the five protons in H5(+) more likely occurs through a stepwise mechanism. Such full permutation of the protons becomes accessible when the shared proton stretch is excited to the vpt = 2 or 3 excited state. The effects of deuteration and rotational excitation of the H2 and H3(+) products are also investigated. Deuteration inhibits permutation of protons, while rotational excitation has only a small impact on these processes.
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Affiliation(s)
- Zhou Lin
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
| | - Anne B McCoy
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
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7
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8
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Affiliation(s)
- Takeshi Oka
- Department of Chemistry and Department of Astronomy and Astrophysics, The Enrico Fermi Institute, University of Chicago , 5801 South Ellis Avenue, Chicago, Illinois 60637, United States
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9
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Hama T, Watanabe N. Surface Processes on Interstellar Amorphous Solid Water: Adsorption, Diffusion, Tunneling Reactions, and Nuclear-Spin Conversion. Chem Rev 2013; 113:8783-839. [DOI: 10.1021/cr4000978] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tetsuya Hama
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
| | - Naoki Watanabe
- Institute of Low Temperature
Science, Hokkaido University, N19W8 Kita-ku, Sapporo, Hokkaido 060-0819, Japan
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10
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Roueff E, Lique F. Molecular Excitation in the Interstellar Medium: Recent Advances in Collisional, Radiative, and Chemical Processes. Chem Rev 2013; 113:8906-38. [DOI: 10.1021/cr400145a] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Evelyne Roueff
- Laboratoire
Univers et Théories, Observatoire de Paris, 92190 Meudon, France
| | - François Lique
- LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 540, 76058 Le Havre, France
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11
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Song H, Lee SY, Yang M, Lu Y. Full-dimensional quantum calculations of the vibrational states of H5(+). J Chem Phys 2013; 138:124309. [PMID: 23556725 DOI: 10.1063/1.4797464] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Full-dimensional quantum calculations of the vibrational states of H5(+) have been performed on the accurate potential energy surface developed by Xie et al. [J. Chem. Phys. 122, 224307 (2005)]. The zero point energies of H5(+), H4D(+), D4H(+), and D5(+) and their ground-state geometries are presented and compared with earlier theoretical results. The first 10 low-lying excited states of H5(+) are assigned to the fundamental, overtone, and combination of the H2-H3(+) stretch, the shared proton hopping and the out-of-plane torsion. The ground-state torsional tunneling splitting, the fundamental of the photon hopping mode and the first overtone of the torsion mode are 87.3 cm(-1), 354.4 cm(-1), and 444.0 cm(-1), respectively. All of these values agree well with the diffusion Monte Carlo and multi-configuration time-dependent Hartree results where available.
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Affiliation(s)
- Hongwei Song
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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12
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Nakashima H, Nakatsuji H. Non-Born-Oppenheimer potential energy curve: Hydrogen molecular ion with highly accurate free complement method. J Chem Phys 2013; 139:074105. [PMID: 23968070 DOI: 10.1063/1.4818161] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although the concept of a potential energy curve (PEC) originates from the outgrowth of the Born-Oppenheimer (BO) approximation, we propose the application of analysis methods for the physical PEC with non-Born-Oppenheimer (non-BO) wave functions. A numerical examination was performed with the highly accurate non-BO vibronic wave functions of hydrogen molecular ion, which were obtained in our previous studies with the free complement method. The reduced density function integrated over the electron coordinates plays an important role in understanding nuclear motion dynamics, since it corresponds to the wave function density of the vibrational and rotational motions. The maximum positions of this density indicate the high existence probability of nuclei and can be considered as a discrete representation of the PEC. Whereas an ordinary PEC with the BO approximation is obtained as a numeric curve after multiple electronic state calculations at fixed nuclear coordinates, we propose a new analytical expression of the PEC from a non-BO wave function.
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Affiliation(s)
- Hiroyuki Nakashima
- Quantum Chemistry Research Institute, JST, CREST, Kyodai Katsura Venture Plaza 107, Goryo Oohara 1-36, Nishikyo-ku, Kyoto 615-8245, Japan.
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13
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Gerin M, de Luca M, Lis DC, Kramer C, Navarro S, Neufeld D, Indriolo N, Godard B, Le Petit F, Peng R, Phillips TG, Roueff E. Determination of the Ortho to Para Ratio of H2Cl+ and H2O+ from Submillimeter Observations. J Phys Chem A 2013; 117:10018-26. [DOI: 10.1021/jp4004533] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maryvonne Gerin
- LERMA, Observatoire de Paris, ENS, and UMR8112 du CNRS, 24 rue Lhomond,
Paris 75231 cedex 05, France
| | - Massimo de Luca
- LERMA, Observatoire de Paris, ENS, and UMR8112 du CNRS, 24 rue Lhomond,
Paris 75231 cedex 05, France
| | - Dariusz C. Lis
- MC301-17, Cahill Center for
Astronomy and Astrophysics, CalTech, Pasadena,
California 91125, United States
| | - Carsten Kramer
- IRAM, Instituto de RadioAstronomìa Milimétrica, Avenida Divina
Pastora, 7, Núcleo CentralE 18012 Granada, Spain
| | - Santiago Navarro
- IRAM, Instituto de RadioAstronomìa Milimétrica, Avenida Divina
Pastora, 7, Núcleo CentralE 18012 Granada, Spain
| | - David Neufeld
- Department of Physics
and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Nick Indriolo
- Department of Physics
and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Benjamin Godard
- LUTH, Observatoire de Paris and UMR8102 du CNRS, Place J. Janssen, 92190
Meudon, France
| | - Franck Le Petit
- LUTH, Observatoire de Paris and UMR8102 du CNRS, Place J. Janssen, 92190
Meudon, France
| | - Ruisheng Peng
- MC301-17, Cahill Center for
Astronomy and Astrophysics, CalTech, Pasadena,
California 91125, United States
| | - Thomas G. Phillips
- MC301-17, Cahill Center for
Astronomy and Astrophysics, CalTech, Pasadena,
California 91125, United States
| | - Evelyne Roueff
- LUTH, Observatoire de Paris and UMR8102 du CNRS, Place J. Janssen, 92190
Meudon, France
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Affiliation(s)
- Kyle N. Crabtree
- Harvard−Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts
02138, United States
| | - Benjamin J. McCall
- Departments
of Chemistry, Astronomy, and Physics, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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15
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Chen HC, Hsiao CY, Peng JL, Amano T, Shy JT. High-resolution sub-Doppler Lamb dips of the ν2 fundamental band of H3(+). PHYSICAL REVIEW LETTERS 2012; 109:263002. [PMID: 23368556 DOI: 10.1103/physrevlett.109.263002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Indexed: 06/01/2023]
Abstract
The high-resolution sub-Doppler Lamb dips of the ν2 fundamental band transitions of H3(+) have been observed using an extended negative glow discharge tube as an ion source and a periodically poled lithium niobate optical parametric oscillator as a radiation source. The absolute frequency of the R(1,0) transition was measured to be 81,720,371.550 MHz with an accuracy of 250 kHz using an optical frequency comb. In addition, we have investigated the linewidth of the Lamb-dip signal of the R(3,0) transition systematically and obtained its pressure-broadening parameter, which may shed some light on the reaction of H3(+) with H2. This is the first observation of the infrared saturated spectrum and the first determination of the pressure-broadening parameter of the ro-vibrational transitions of a molecular ion.
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Affiliation(s)
- Hsuan-Chen Chen
- Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan
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16
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Kluge L, Gärtner S, Brünken S, Asvany O, Gerlich D, Schlemmer S. Transfer of a proton between H2 and O2. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:5041-5054. [PMID: 23028152 DOI: 10.1098/rsta.2012.0170] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The proton affinities of hydrogen and oxygen are very similar. Therefore, it has been discussed that the proton transfer from the omnipresent H(3)(+) to molecular oxygen in the near thermoneutral reaction H(3)(+) + O(2) <--> O(2)H(+) + H(2) effectively binds the interstellar oxygen in O(2)H(+). In this work, the proton transfer reaction has been investigated in a low-temperature 22-pole ion trap from almost room temperature (280 K) down to the lowest possible temperature limited by freeze out of oxygen gas (about 40 K at a low pressure). The Arrhenius behaviour of the rate coefficient for the forward reaction shows that it is subject to an activation energy of E(A)/k=113 K. Thus, the forward reaction can proceed only in higher temperature molecular clouds. Applying laser-induced reactions to the given reaction (in the backward direction), a preliminary search for spectroscopic signatures of O(2)H(+) in the infrared was unsuccessful, whereas the forward reaction has been successfully used to probe the population of the lowest ortho and para levels of H(3)(+).
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Affiliation(s)
- Lars Kluge
- I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
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17
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Crabtree KN, McCall BJ. The ortho : para ratio of H3+ in laboratory and astrophysical plasmas. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:5055-5065. [PMID: 23028153 DOI: 10.1098/rsta.2012.0016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In diffuse molecular clouds, the nuclear spin temperature of H(3)(+) (approx. 30 K) is much lower than the cloud kinetic temperature (approx. 70 K). To understand this temperature discrepancy, we have measured the ratio of the hop to exchange pathways (α) in the H(3)(+) + H(2) --> H(2) + H(3)(+) reaction (which interconverts ortho- and para-H(3)(+)) using high-resolution spectroscopy of the ν(2) fundamental band of H(3)(+) in a hydrogenic plasma. We find that α decreases from 1.6±0.1 at 350 K to its statistical value of 0.5±0.1 at 135 K. We use this result to model the steady-state chemistry of diffuse molecular clouds, finding good agreement with astronomical data provided the dissociative recombination rates of ortho- and para-H(3)(+) are equal and the identity branching fraction for the H(3)(+) + H(2) reaction is large. Our results highlight the need for further studies of the H(3)(+) + H(2) reaction as well as state-selective measurements of H(3)(+) dissociative recombination.
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Affiliation(s)
- Kyle N Crabtree
- Department of Chemistry, University of Illinois, Urbana, IL 61801, USA
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18
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Oka T. Chemistry, astronomy and physics of H3+. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:4991-5000. [PMID: 23028148 PMCID: PMC3479714 DOI: 10.1098/rsta.2012.0243] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The great developments in the chemistry, astronomy and physics of H(3)(+) since 2006, which have led to this Royal Society Theo Murphy Meeting, are reviewed.
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Affiliation(s)
- Takeshi Oka
- Department of Astronomy and Astrophysics, The Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, USA.
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19
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Pagani L, Lesaffre P, Roueff E, Jorfi M, Honvault P, González-Lezana T, Faure A. H2, H3+ and the age of molecular clouds and prestellar cores. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:5200-5212. [PMID: 23028166 DOI: 10.1098/rsta.2012.0027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Measuring the age of molecular clouds and prestellar cores is a difficult task that has not yet been successfully accomplished although the information is of paramount importance to help in understanding and discriminating between different formation scenarios. Most chemical clocks suffer from unknown initial conditions and are therefore difficult to use. We propose a new approach based on a subset of deuterium chemistry that takes place in the gas phase and for which initial conditions are relatively well known. It relies primarily on the conversion of H(3)(+) into H(2)D(+) to initiate deuterium enrichment of the molecular gas. This conversion is controlled by the ortho/para ratio of H(2) that is thought to be produced with the statistical ratio of 3 and subsequently slowly decays to an almost pure para-H(2) phase. This slow decay takes approximately 1 Myr and allows us to set an upper limit on the age of molecular clouds. The deuterium enrichment of the core takes longer to reach equilibrium and allows us to estimate the time necessary to form a dense prestellar core, i.e. the last step before the collapse of the core into a protostar. We find that the observed abundance and distribution of DCO(+) and N(2)D(+) argue against quasi-static core formation and favour dynamical formation on time scales of less than 1 Myr. Another consequence is that ortho-H(2) remains comparable to para-H(2) in abundance outside the dense cores.
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Affiliation(s)
- L Pagani
- LERMA, UMR8112 du CNRS, Observatoire de Paris, 61, Av. de l'Observatoire, 75014 Paris, France.
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Gómez-Carrasco S, González-Sánchez L, Aguado A, Sanz-Sanz C, Zanchet A, Roncero O. Dynamically biased statistical model for the ortho/para conversion in the H2+H3+ → H3++ H2 reaction. J Chem Phys 2012; 137:094303. [DOI: 10.1063/1.4747548] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dohnal P, Hejduk M, Varju J, Rubovič P, Roučka Š, Kotrík T, Plašil R, Glosík J, Johnsen R. Binary and ternary recombination of para-H3+ and ortho-H3+ with electrons: State selective study at 77–200 K. J Chem Phys 2012; 136:244304. [DOI: 10.1063/1.4730162] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Crabtree KN, Kauffman CA, Tom BA, Beçka E, McGuire BA, McCall BJ. Nuclear spin dependence of the reaction of H3+ with H2. II. Experimental measurements. J Chem Phys 2011; 134:194311. [DOI: 10.1063/1.3587246] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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