1
|
von Haeften K, Laarmann T, Wabnitz H, Möller T. Relaxation dynamics of 3He and 4He clusters and droplets studied using near infrared and visible fluorescence excitation spectroscopy. Phys Chem Chem Phys 2023; 25:1863-1880. [PMID: 36541224 DOI: 10.1039/d2cp04594j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The relaxation dynamics of electronically excited 3He and 4He clusters and droplets is investigated using time-correlated near-infrared and visible (NIR/VIS) fluorescence excitation spectroscopy. A rich data set spanning a wide range of cluster and droplet sizes is produced. The spectral features broadly follow the vacuum ultraviolet excitation (VUV) spectra. However, when the NIR/VIS spectra are normalised to the VUV fluorescence, regions with distinctly different cluster size and isotope dependence are identified, enabling deeper insight into the relaxation mechanism. Particle density, location of atomic-like states and their principal quantum number, n, are found to play an important role in the relaxation. For states with n = 3 and higher, only energy within the surface region is transferred to excited atoms which are subsequently ejected from the surface and fluoresce in vacuum. For states with n = 2, energy from the entire region within clusters and droplets is transferred to the surface, leading to the ejection of excited atoms and excimers. Here, the energy is transferred by excitation hopping, which competes with radiative and non-radiative decay, making ejection and NIR/VIS fluorescence inefficient in increasingly larger droplets.
Collapse
|
2
|
Kazak L, Meiwes-Broer KH, Tiggesbäumker J. Ionization potentials of Mg N ( N = 7-56) clusters formed by spontaneous collapse of magnesium foam in helium nanodroplets. Phys Chem Chem Phys 2022; 24:23350-23356. [PMID: 36134466 DOI: 10.1039/d2cp03075f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ionization potentials of magnesium clusters (MgN, N = 7-56) are determined by doping ultracold helium nanodroplets (HeM, M ≈ 52 000) with Mg atoms. Inspecting the particle size distributions resulting from non-resonant, short-wavelength, single-photon ionization gives evidence that beyond a certain ensemble size, the developing foam structure undergoes a spontaneous collapse on the way to the laser interaction region. As a result, hot Mg clusters form in the relaxation process. The spontaneous collapse manifests in a substantial change in the size distributions, when recording mass spectra at wavelengths shorter than 272 nm. Tracing individual MgN signals as a function of laser photon energy allows extraction of size-specific ionization potentials, which for small clusters show a good agreement with results obtained from density functional theory simulations. The further development is compared to calculations based on the liquid drop model. However, even when quantum effects are included, the simple scaling law is not able to reproduce the development of the ionization potentials. The results suggest that small neutral magnesium clusters behave as non-metallic. The comparison to electron affinities and band gaps obtained from photoemission experiments on MgN- provides information on the charge state dependence of the non-metal-to-metal transition and properties like the Mulliken electron negativity.
Collapse
Affiliation(s)
- Lev Kazak
- Institute of Physics, University of Rostock, 18059, Rostock, Germany.
| | - Karl-Heinz Meiwes-Broer
- Institute of Physics, University of Rostock, 18059, Rostock, Germany. .,Department "Life, Light and Matter", University of Rostock, 18059, Rostock, Germany
| | - Josef Tiggesbäumker
- Institute of Physics, University of Rostock, 18059, Rostock, Germany. .,Department "Life, Light and Matter", University of Rostock, 18059, Rostock, Germany
| |
Collapse
|
3
|
Shaik S, Danovich D, Hiberty PC. On The Nature of the Chemical Bond in Valence Bond Theory. J Chem Phys 2022; 157:090901. [DOI: 10.1063/5.0095953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This perspective outlines a panoramic description of the nature of the chemical bond according to valence bond theory. It describes single bonds, and charge-shift bonds (CSBs) in which the entire/most of the bond energy arises from the resonance between the covalent and ionic structures of the bond. Many CSBs are homonuclear bonds. Hypervalent molecules are CSBs. Then we describe multiply bonded molecules with emphasis on C2 and 3O2. The perspective outlines an effective methodology of peeling the electronic structure to the necessary minimum: a structure with a quadruple bond, and two minor structures with double bonds, which stabilize the quadruple bond by resonance. 3O2 is chosen because it is a persistent diradical. The persistence of 3O2 is due to the large CSB resonance interaction of the π-3-electron bonds. Subsequently, we describe the roles of π vs. σ in the geometric preferences in unsaturated molecules, and their Si-based analogs. Then, the perspective discusses bonding in clusters of univalent metal-atoms, which possess only parallel spins, and are nevertheless bonded due to multiple resonance interactions. The bond energy reaches ~40 kcal/mol for a pair of atoms (in n+1Cun; n~10-12). The final subsection discusses singlet excited states in ethene, ozone and SO2. It demonstrates the capability of the breathing-orbital VB method to yield an accurate description of a variety of excited states using 10 or less VB structures. Furthermore, the method underscores covalent structures which play a key role in the correct description and bonding of these excited states.
Collapse
Affiliation(s)
- Sason Shaik
- Hebrew University of Jerusalem Institute of Chemistry, Israel
| | - David Danovich
- Hebrew University of Jerusalem Institute of Chemistry, Israel
| | | |
Collapse
|
4
|
Albertini S, Gruber E, Zappa F, Krasnokutski S, Laimer F, Scheier P. Chemistry and physics of dopants embedded in helium droplets. MASS SPECTROMETRY REVIEWS 2022; 41:529-567. [PMID: 33993543 DOI: 10.1002/mas.21699] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 05/18/2023]
Abstract
Helium droplets represent a cold inert matrix, free of walls with outstanding properties to grow complexes and clusters at conditions that are perfect to simulate cold and dense regions of the interstellar medium. At sub-Kelvin temperatures, barrierless reactions triggered by radicals or ions have been observed and studied by optical spectroscopy and mass spectrometry. The present review summarizes developments of experimental techniques and methods and recent results they enabled.
Collapse
Affiliation(s)
- Simon Albertini
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Elisabeth Gruber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Serge Krasnokutski
- Laboratory Astrophysics Group of the MPI for Astronomy, University of Jena, Jena, Germany
| | - Felix Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| |
Collapse
|
5
|
Kelbg M, Zabel M, Krebs B, Kazak L, Meiwes-Broer KH, Tiggesbäumker J. Temporal Development of a Laser-Induced Helium Nanoplasma Measured through Auger Emission and Above-Threshold Ionization. PHYSICAL REVIEW LETTERS 2020; 125:093202. [PMID: 32915628 DOI: 10.1103/physrevlett.125.093202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 04/14/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
Femtosecond pump-probe electron and ion spectroscopy is applied to study the development of a helium nanoplasma up to the nanosecond timescale. Electrons, bound by the deep confining mean-field potential, are elevated toward the vacuum level in the nanoplasma expansion. Subsequent electron recombination gives rise to transitions between He^{+} states, resulting in autoionization. The time-resolved analysis of the energy transfer to quasifree electrons reveals a transient depletion of the Auger emission, which allows for a temporal gate to map the distribution of delocalized electrons in the developing mean field. Furthermore, we trace the recombination of delocalized electrons near the vacuum level into highly excited Rydberg states. Transient above-threshold ionization is introduced as a diagnostic tool to resolve the dynamics. Thus, the development of the electron distribution in the nanoplasma mean-field potential can be monitored via the features observed in the emission spectra.
Collapse
Affiliation(s)
- M Kelbg
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - M Zabel
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - B Krebs
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - L Kazak
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - K-H Meiwes-Broer
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany and Department "Life, Light, and Matter," Universität Rostock, 18059 Rostock, Germany
| | - J Tiggesbäumker
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany and Department "Life, Light, and Matter," Universität Rostock, 18059 Rostock, Germany
| |
Collapse
|
6
|
González-Lezana T, Echt O, Gatchell M, Bartolomei M, Campos-Martínez J, Scheier P. Solvation of ions in helium. INT REV PHYS CHEM 2020. [DOI: 10.1080/0144235x.2020.1794585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Tomás González-Lezana
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Olof Echt
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, University of New Hampshire, Durham, NH, USA
| | - Michael Gatchell
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - Massimiliano Bartolomei
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - José Campos-Martínez
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas IFF-CSIC, Madrid, Spain
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| |
Collapse
|
7
|
Brieuc F, Schran C, Uhl F, Forbert H, Marx D. Converged quantum simulations of reactive solutes in superfluid helium: The Bochum perspective. J Chem Phys 2020; 152:210901. [DOI: 10.1063/5.0008309] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Fabien Brieuc
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Christoph Schran
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Felix Uhl
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Harald Forbert
- Center for Solvation Science ZEMOS, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
| |
Collapse
|
8
|
Lasserus M, Knez D, Lackner F, Schnedlitz M, Messner R, Schennach D, Kothleitner G, Hofer F, Hauser AW, Ernst WE. Synthesis of nanosized vanadium(v) oxide clusters below 10 nm. Phys Chem Chem Phys 2019; 21:21104-21108. [PMID: 31528952 DOI: 10.1039/c9cp04357h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vanadium oxide clusters with a mean diameter below 10 nm are investigated by high resolution Scanning Transmission Electron Microscopy (STEM), Electron Energy Loss Spectroscopy (EELS) and UV-vis absorption spectroscopy. The clusters are synthesised by sublimation from bulk vanadium(v) oxide, in combination with a pick-up by superfluid helium droplets. The latter act as reaction chambers which enable cluster growth under fully inert and solvent-free conditions. High-resolution STEM images of deposited vanadium oxide particles allowing for the determination of lattice constants, clearly indicate a dominating presence of V2O5. This finding is further supported by UV-vis absorption spectra of nanoparticles after deposition on fused silica substrates, which indicates that the oxidation state of the material is preserved over the entire process. From the results of the UV-vis measurement, the band gap of the nanosized V2O5 could be determined to be 3.3 eV. The synthesis approach provides a route to clean V2O5 clusters as it does not involve any surfactant or solvents, which is crucial for an unbiased measurement of intrinsic catalyst properties.
Collapse
Affiliation(s)
- Maximilian Lasserus
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Daniel Knez
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Daniel Schennach
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Gerald Kothleitner
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
| | - Ferdinand Hofer
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
| | - Andreas W Hauser
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| |
Collapse
|
9
|
Kazak L, Göde S, Meiwes-Broer KH, Tiggesbäumker J. Photoelectron Spectroscopy on Magnesium Ensembles in Helium Nanodroplets. J Phys Chem A 2019; 123:5951-5956. [DOI: 10.1021/acs.jpca.9b02880] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
10
|
Kelbg M, Zabel M, Krebs B, Kazak L, Meiwes-Broer KH, Tiggesbäumker J. Auger emission from the Coulomb explosion of helium nanoplasmas. J Chem Phys 2019; 150:204302. [DOI: 10.1063/1.5089943] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M. Kelbg
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - M. Zabel
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - B. Krebs
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - L. Kazak
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - K.-H. Meiwes-Broer
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
- Department of Life, Light and Matter, Universität Rostock, 18059 Rostock, Germany
| | - J. Tiggesbäumker
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
- Department of Life, Light and Matter, Universität Rostock, 18059 Rostock, Germany
| |
Collapse
|
11
|
Kelbg M, Heidenreich A, Kazak L, Zabel M, Krebs B, Meiwes-Broer KH, Tiggesbäumker J. Comparison of Electron and Ion Emission from Xenon Cluster-Induced Ignition of Helium Nanodroplets. J Phys Chem A 2018; 122:8107-8113. [PMID: 30239204 DOI: 10.1021/acs.jpca.8b06673] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The charging dynamics of helium droplets driven by embedded xenon cluster ignition in strong laser fields is studied by comparing the abundances of helium and highly charged Xe ions to the electron signal. Femtosecond pump-probe experiments show that near the optimal delay for highly charged xenon the electron yield increases, especially at low energies. The electron signature can be traced back to the ionization of the helium environment by Xe seed electrons. Accompanying molecular dynamics simulations suggest a two-step ionization scenario in the Xe-He core-shell system. In contrast to xenon, the experimental signal of the helium ions, as well as low-energy electron emission show a deviating delay dependence, indicating differences in the temporal and spacial development of the charge state distribution of Xe core and He surrounding. From the pump-probe dependence of the electron emission, effective temperatures can be extracted, indicating the nanoplasma decay.
Collapse
Affiliation(s)
- Michael Kelbg
- Institute of Physics , University of Rostock , Rostock 18059 , Germany
| | - Andreas Heidenreich
- Kimika Fakultatea , Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC) , P.K. 1072, Donostia 20018 , Spain.,IKERBASQUE, Basque Foundation for Science , Bilbao 48013 , Spain
| | - Lev Kazak
- Institute of Physics , University of Rostock , Rostock 18059 , Germany
| | - Michael Zabel
- Institute of Physics , University of Rostock , Rostock 18059 , Germany
| | - Bennet Krebs
- Institute of Physics , University of Rostock , Rostock 18059 , Germany
| | - Karl-Heinz Meiwes-Broer
- Institute of Physics , University of Rostock , Rostock 18059 , Germany.,Department Life, Light and Matter , University of Rostock , Rostock 18059 , Germany
| | - Josef Tiggesbäumker
- Institute of Physics , University of Rostock , Rostock 18059 , Germany.,Department Life, Light and Matter , University of Rostock , Rostock 18059 , Germany
| |
Collapse
|
12
|
|
13
|
Ancilotto F, Barranco M, Coppens F, Eloranta J, Halberstadt N, Hernando A, Mateo D, Pi M. Density functional theory of doped superfluid liquid helium and nanodroplets. INT REV PHYS CHEM 2017. [DOI: 10.1080/0144235x.2017.1351672] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Francesco Ancilotto
- Dipartimento di Fisica e Astronomia ‘Galileo Galilei’ and CNISM, Università di Padova, Padova, Italy
- CNR-IOM Democritos, Trieste, Italy
| | - Manuel Barranco
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - François Coppens
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Jussi Eloranta
- Department of Chemistry and Biochemistry, California State University at Northridge, Northridge, CA, USA
| | - Nadine Halberstadt
- Laboratoire des Collisions, Agrégats et Réactivité, IRSAMC, Université Toulouse 3 and CNRS, Toulouse Cedex 09, France
| | - Alberto Hernando
- Social Thermodynamics Applied Research (SThAR), EPFL Innovation Park, Lausanne, Switzerland
| | - David Mateo
- Applied Complexity Group, Singapore University of Technology and Design, Singapore, Singapore
| | - Martí Pi
- Facultat de Física, Departament FQA, Universitat de Barcelona, Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| |
Collapse
|
14
|
Abstract
As we approach the Lewis model centennial, it may be timely to discuss novel bonding motifs. Accordingly, this review discusses no-pair ferromagnetic (NPFM) bonds that hold together monovalent metallic atoms using exclusively parallel spins. Thus, without any traditional electron-pair bonds, the bonding energy per atom in these clusters can reach 20 kcal mol(-1). This review describes the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that are delocalized over all the close neighbors of a given atom in the cluster. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry and for the very steep rise of the bonding energy per atom. The advent of NPFM clusters offers new horizons in chemistry of highly magnetic species sensitive to magnetic and electric fields.
Collapse
Affiliation(s)
- David Danovich
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University, 91904 Jerusalem, Israel; ,
| |
Collapse
|
15
|
Rodríguez-Cantano R, González-Lezana T, Villarreal P. Path integral Monte Carlo investigations on doped helium clusters. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2015.1132595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
16
|
Gas-Phase Molecular Spectroscopy in the Past Five Decades: Bearings of the Advancements in Light Source Technologies. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES INDIA SECTION A-PHYSICAL SCIENCES 2015. [DOI: 10.1007/s40010-015-0252-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
17
|
He Y, Zhang J, Li Y, Freund WM, Kong W. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:084102. [PMID: 26329210 PMCID: PMC4537483 DOI: 10.1063/1.4928107] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 07/25/2015] [Indexed: 05/29/2023]
Abstract
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.
Collapse
Affiliation(s)
- Yunteng He
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Yang Li
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
18
|
Chen L, Zhang J, Freund WM, Kong W. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets. J Chem Phys 2015; 143:044310. [PMID: 26233132 PMCID: PMC4522010 DOI: 10.1063/1.4927471] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/15/2015] [Indexed: 11/14/2022] Open
Abstract
We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs(+) is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs(+)-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10(6) helium atoms when the source temperature is between 14 K and 17 K.
Collapse
Affiliation(s)
- Lei Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - William M Freund
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| |
Collapse
|
19
|
Hauser AW, Volk A, Thaler P, Ernst WE. Atomic collisions in suprafluid helium-nanodroplets: timescales for metal-cluster formation derived from He-density functional theory. Phys Chem Chem Phys 2015; 17:10805-12. [PMID: 25812719 PMCID: PMC4441260 DOI: 10.1039/c5cp01110h] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 03/17/2015] [Indexed: 11/21/2022]
Abstract
Collision times for the coinage metal atoms Cu, Ag and Au in He-droplets are derived from helium density functional theory and molecular dynamics simulations. The strength of the attractive interaction between the metal atoms turns out to be less important than the mass of the propagating metal atoms. Even for small droplets consisting of a few thousand helium atoms, the collision times are shortest for Cu, followed by Ag and Au, despite the higher binding energy of Au2 compared to Cu2.
Collapse
Affiliation(s)
- Andreas W. Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Alexander Volk
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Philipp Thaler
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| | - Wolfgang E. Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ;
| |
Collapse
|
20
|
Koch M, Kautsch A, Lackner F, Ernst WE. One- and two-color resonant photoionization spectroscopy of chromium-doped helium nanodroplets. J Phys Chem A 2014; 118:8373-9. [PMID: 24708058 PMCID: PMC4166682 DOI: 10.1021/jp501285r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We investigate the photoinduced relaxation
dynamics of Cr atoms
embedded into superfluid helium nanodroplets. One- and two-color resonant
two-photon ionization (1CR2PI and 2CR2PI, respectively) are applied
to study the two strong ground state transitions z7P2,3,4° ←
a7S3 and y7P2,3,4° ← a7S3. Upon photoexcitation, Cr* atoms are ejected from the
droplet in various excited states, as well as paired with helium atoms
as Cr*–Hen exciplexes. For the
y7P2,3,4° intermediate state, comparison of the two methods reveals
that energetically lower states than previously identified are also
populated. With 1CR2PI we find that the population of ejected z5P3° states is reduced for increasing droplet size, indicating that population
is transferred preferentially to lower states during longer interaction
with the droplet. In the 2CR2PI spectra we find evidence for generation
of bare Cr atoms in their septet ground state (a7S3) and metastable quintet state (a5S2), which we attribute to a photoinduced fast excitation–relaxation
cycle mediated by the droplet. A fraction of Cr atoms in these ground
and metastable states is attached to helium atoms, as indicated by
blue wings next to bare atom spectral lines. These relaxation channels
provide new insight into the interaction of excited transition metal
atoms with helium nanodroplets.
Collapse
Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria
| | | | | | | |
Collapse
|
21
|
Mateo D, Gonzalez F, Eloranta J. Rotational Superfluidity in Small Helium Droplets. J Phys Chem A 2014; 119:2262-70. [DOI: 10.1021/jp5057286] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David Mateo
- Department
of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Frisly Gonzalez
- Department
of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Jussi Eloranta
- Department
of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| |
Collapse
|
22
|
Lindebner F, Kautsch A, Koch M, Ernst WE. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2014; 365-366:255-259. [PMID: 25844053 PMCID: PMC4376070 DOI: 10.1016/j.ijms.2013.12.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 06/04/2023]
Abstract
Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P[Formula: see text]S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cu n clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy.
Collapse
|
23
|
Yang S, Ellis AM, Spence D, Feng C, Boatwright A, Latimer E, Binns C. Growing metal nanoparticles in superfluid helium. NANOSCALE 2013; 5:11545-11553. [PMID: 24107922 DOI: 10.1039/c3nr04003h] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Helium droplets provide a cold and confined environment where atomic and/or molecular dopants can aggregate into clusters and nanoparticles. In particular, the sequential addition of different materials to helium droplets can lead to the formation of a wide range of nanoparticles, including core-shell nanoparticles, which can then be deposited onto a surface. Here we briefly discuss the fundamental properties of helium droplets and then address their implications for the formation of clusters and nanoparticles. Several key experiments on atomic and molecular clusters will be highlighted and new results obtained for nanoparticles formed in this way will be presented. Finally, the versatility, the limitations and new possibilities provided by superfluid helium droplets in nanoscience and nanotechnology will be addressed.
Collapse
Affiliation(s)
- Shengfu Yang
- Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
| | | | | | | | | | | | | |
Collapse
|
24
|
Volk A, Thaler P, Koch M, Fisslthaler E, Grogger W, Ernst WE. High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets. J Chem Phys 2013; 138:214312. [PMID: 23758376 DOI: 10.1063/1.4807843] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Alexander Volk
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | | | | | | | | | | |
Collapse
|
25
|
Mateo D, Hernando A, Barranco M, Loginov E, Drabbels M, Pi M. Translational dynamics of photoexcited atoms in 4He nanodroplets: the case of silver. Phys Chem Chem Phys 2013; 15:18388-400. [DOI: 10.1039/c3cp52221k] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
26
|
|
27
|
Abstract
Helium droplets spanning a wide size range, N(He) = 10(3)-10(10), were formed in a continuous-nozzle beam expansion at different nozzle temperatures and a constant stagnation pressure of 20 bars. The average sizes of the droplets have been obtained by attenuation of the droplet beam through collisions with argon and helium gases at room temperature. The results obtained are in good agreement with previous measurements in the size range N(He) = 10(5)-10(7). Moreover, the measurements give the average sizes in the previously uncharacterized range of very large droplets of 10(7)-10(10) atoms. The droplet sizes and beam flux increase rapidly at nozzle temperatures below 6 K, which is ascribed to the formation of droplets within the nozzle interior. The mass spectra of the droplet beam upon electron impact ionization have also been obtained. The spectra show a large increase in the intensity of the He(4) (+) signal upon increase of the droplet size, an effect which can be used as a secondary size standard in the droplet size range N(He) = 10(4)-10(9) atoms.
Collapse
Affiliation(s)
- Luis F Gomez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | | | | | | |
Collapse
|
28
|
Mella M. Higher order diffusion Monte Carlo propagators for linear rotors as diffusion on a sphere: development and application to O2@He(n). J Chem Phys 2011; 135:114504. [PMID: 21950868 DOI: 10.1063/1.3639190] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exploiting the theoretical treatment of particles diffusing on corrugated surfaces and the isomorphism between the "particle on a sphere" and a linear molecule rotation, a new diffusion kernel is introduced to increase the order of diffusion Monte Carlo (DMC) simulations involving linear rotors. Tests carried out on model systems indicate the superior performances of the new rotational diffusion kernel with respect to the simpler alternatives previously employed. In particular, it is evidenced a second order convergence toward exact results with respect to the time step of dynamical correlation functions, a fact that guarantees an identical order for the diffusion part of the DMC projector. The algorithmic advantages afforded by the latter are discussed, especially with respect to the "a posteriori" and "on the fly" extrapolation schemes. As a first application to the new algorithm, the structure and energetics of O(2)@He(n) (n = 1-40) clusters have been studied. This was done to investigate the possible cause of the quenching of the reaction between O(2) and Mg witnessed upon increasing the size of superfluid He droplets used as a solvent. With the simulations on O(2) indicating a strong localization in the cluster core, the behaviour as a function of n is ascribed to the extremely fluxional comportment of Mg@He(n), which dwells far from the droplet center, albeit being solvated, when n is large.
Collapse
Affiliation(s)
- Massimo Mella
- Dipartimento di Scienze Chimiche ed Ambientali, Università degli Studi dell'Insubria, via Lucini 3, 22100 Como, Italy.
| |
Collapse
|
29
|
Christen W, Radcliffe P, Przystawik A, Diederich T, Tiggesbäumker J. Argon Solvent Effects on Optical Properties of Silver Metal Clusters. J Phys Chem A 2011; 115:8779-82. [DOI: 10.1021/jp200487s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- W. Christen
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany, and
| | - P. Radcliffe
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - A. Przystawik
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - Th. Diederich
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - J. Tiggesbäumker
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| |
Collapse
|
30
|
Liang T, Flynn SD, Morrison AM, Douberly GE. Quantum Cascade Laser Spectroscopy and Photoinduced Chemistry of Al–(CO)n Clusters in Helium Nanodroplets. J Phys Chem A 2011; 115:7437-47. [DOI: 10.1021/jp203367t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tao Liang
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Steven D. Flynn
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Alexander M. Morrison
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Gary E. Douberly
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| |
Collapse
|
31
|
Loginov E, Gomez LF, Vilesov AF. Surface Deposition and Imaging of Large Ag Clusters Formed in He Droplets. J Phys Chem A 2011; 115:7199-204. [DOI: 10.1021/jp200198n] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Evgeny Loginov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Luis F. Gomez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Andrey F. Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| |
Collapse
|
32
|
Callegari C, Ancilotto F. Perturbation Method to Calculate the Interaction Potentials and Electronic Excitation Spectra of Atoms in He Nanodroplets. J Phys Chem A 2011; 115:6789-96. [PMID: 21434657 DOI: 10.1021/jp111157w] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Carlo Callegari
- Institute of Experimental Physics, TU Graz, Petersgasse 16, A-8010 Graz, Austria, EU
| | - Francesco Ancilotto
- Dipartimento di Fisica ‘G. Galilei’, Università di Padova, via Marzolo 8, I-35131 Padova, Italy
- CNR-IOM-Democritos, I-34136 Trieste, Italy
| |
Collapse
|
33
|
Cargnoni F, Mella M. Solubility of Metal Atoms in Helium Droplets: Exploring the Effect of the Well Depth Using the Coinage Metals Cu and Ag. J Phys Chem A 2011; 115:7141-52. [PMID: 21425774 DOI: 10.1021/jp112408d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Massimo Mella
- School of Chemistry, Cardiff University, Main Building, CF10 3AT Cardiff, United Kingdom
- Dipartimento di Scienze Chimiche ed Ambientali, Università degli Studi dell’Insubria, via Lucini 3, 22100 Como (I), Italy
| |
Collapse
|
34
|
Brahms N, Tscherbul TV, Zhang P, Kłos J, Forrey RC, Au YS, Sadeghpour HR, Dalgarno A, Doyle JM, Walker TG. Formation and dynamics of van der Waals molecules in buffer-gas traps. Phys Chem Chem Phys 2011; 13:19125-41. [DOI: 10.1039/c1cp21317b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
35
|
Lebedev V, Moroshkin P, Toennies JP, Weis A. Spectroscopy of the copper dimer in normal fluid, superfluid, and solid H4e. J Chem Phys 2010; 133:154508. [DOI: 10.1063/1.3497643] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
36
|
Döppner T, Müller JP, Przystawik A, Göde S, Tiggesbäumker J, Meiwes-Broer KH, Varin C, Ramunno L, Brabec T, Fennel T. Steplike intensity threshold behavior of extreme ionization in laser-driven xenon clusters. PHYSICAL REVIEW LETTERS 2010; 105:053401. [PMID: 20867915 DOI: 10.1103/physrevlett.105.053401] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Indexed: 05/29/2023]
Abstract
The generation of highly charged Xe(q+) ions up to q=24 is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses (λ=800 nm). Laser intensity resolved measurements show that the high-q ion generation starts at an unexpectedly low threshold intensity of about 10(14) W/cm2. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.
Collapse
Affiliation(s)
- T Döppner
- Institut für Physik, Universität Rostock, 18051 Rostock, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Kornilov O, Wang CC, Bünermann O, Healy AT, Leonard M, Peng C, Leone SR, Neumark DM, Gessner O. Ultrafast Dynamics in Helium Nanodroplets Probed by Femtosecond Time-Resolved EUV Photoelectron Imaging. J Phys Chem A 2009; 114:1437-45. [DOI: 10.1021/jp907312t] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Oleg Kornilov
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Chia C. Wang
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Oliver Bünermann
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Andrew T. Healy
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Mathew Leonard
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Chunte Peng
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Stephen R. Leone
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Daniel M. Neumark
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| | - Oliver Gessner
- Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, University of California, Berkeley, California 94720
| |
Collapse
|
38
|
Tong XF, Yang CL, An YP, Wang MS, Ma XG, Wang DH. Theoretical characteristics of the bound states of M-X complexes (M=Cu, Ag, and Au, and X=He, Ne, and Ar). J Chem Phys 2009; 131:244304. [DOI: 10.1063/1.3274815] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
|
39
|
Koch M, Lanzersdorfer J, Callegari C, Muenter JS, Ernst WE. Molecular Beam Magnetic Resonance in Doped Helium Nanodroplets. A Setup for Optically Detected ESR/NMR in the Presence of Unresolved Zeeman Splittings. J Phys Chem A 2009; 113:13347-56. [PMID: 19921944 DOI: 10.1021/jp9041827] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU, and Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | - Johannes Lanzersdorfer
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU, and Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | - Carlo Callegari
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU, and Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | - John S. Muenter
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU, and Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU, and Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| |
Collapse
|
40
|
Alves SG, Vilesov AF, Ferreira SC. Effects of the mean free path and relaxation in a model for the aggregation of particles in superfluid media. J Chem Phys 2009; 130:244506. [DOI: 10.1063/1.3158359] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
|
41
|
Cargnoni F, Kuś T, Mella M, Bartlett RJ. Ground state potential energy surfaces and bound states of M-He dimers (M=Cu,Ag,Au): a theoretical investigation. J Chem Phys 2008; 129:204307. [PMID: 19045864 DOI: 10.1063/1.3020706] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We present an ab initio investigation on the ground state interaction potentials [potential energy surface (PES)] between helium and the group 11 metal atoms: copper, silver, and gold. To the best of our knowledge, there are no previous theoretical PESs proposed for Cu-He and Au-He, and a single one for Ag-He [Z. J. Jakubek and M. Takami, Chem. Phys. Lett. 265, 653 (1997)], computed about 10 years ago at MP2 level and significantly improved by our study. To reach a high degree of accuracy in the determination of the three M-He potentials (M=Cu,Ag,Au), we performed extensive series of test computations to establish the appropriate basis set, the theoretical method, and the computational scheme for these systems. For each M-He dimer we computed the PES at the CCSD(T) level of theory, starting from the reference unrestricted Hartree-Fock wave function. We described the inner shells with relativistic small core pseudopotentials, and we adopted high quality basis sets for the valence electrons. We also performed CCSDT computations in a limited set of M-He internuclear distances, adopting a medium-sized basis set, such as to define for each dimer a CCSD(T) to CCSDT correction term and to improve further the quality of the CCSD(T) interaction potentials. The Cu-He complex has minimum interaction energy (E(min)) of -28.4 microhartree at the internuclear distance of 4.59 A (R(min)), and the short-range repulsive wall starts at 4.04 A (R(E=0)). Quite interestingly, the PES of Ag-He is more attractive (E(min)=-33.8 microhartree) but presents nearly the same R(min) and R(E=0) values, 4.60 and 4.04 A, respectively. The interaction potential for Au-He is markedly deeper and shifted at shorter distances as compared to the lighter complexes, with E(min)=-69.6 microhartree, R(min)=4.09 A and R(E=0)=3.60 A. As a first insight in the structure of M-He(n) aggregates, we determined the rovibrational structure of the three M-He dimers. The Cu-He and Ag-He potentials support just few rotational excitations, while the Au-He PES admits also a bound vibrational excitation.
Collapse
|
42
|
Shigeyasu M, Murayama H, Tanaka H. Production of nanoparticles composed of ionic liquid [C4mpyrr][NTf2] and their chemical identification by diameter analysis and X-ray photoelectron spectroscopy. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.08.068] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
43
|
Szalewicz K. Interplay between theory and experiment in investigations of molecules embedded in superfluid helium nanodroplets†. INT REV PHYS CHEM 2008. [DOI: 10.1080/01442350801933485] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
44
|
Patkowski K, Podeszwa R, Szalewicz K. Interactions in Diatomic Dimers Involving Closed-Shell Metals. J Phys Chem A 2007; 111:12822-38. [DOI: 10.1021/jp076412c] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Konrad Patkowski
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716
| | - Rafał Podeszwa
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716
| | - Krzysztof Szalewicz
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716
| |
Collapse
|
45
|
Mozhayskiy V, Slipchenko MN, Adamchuk VK, Vilesov AF. Use of helium nanodroplets for assembly, transport, and surface deposition of large molecular and atomic clusters. J Chem Phys 2007; 127:094701. [PMID: 17824753 DOI: 10.1063/1.2759927] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The utility of continuous beam of helium droplets for assembly, transport, and surface deposition of metal and molecular clusters is studied. Clusters of propyne having from about 10 to 10(4) molecules were obtained via sequential pickup of molecules by He droplets with average sizes in the range of 10(4)-10(7) atoms. The maximum attainable flux of the propyne molecules carried by He droplets was found to be in the range of (5-15)x10(15) molecules sr(-1) s(-1), being larger in larger droplets. The size of the clusters and the flux of the transported species are ultimately limited by the evaporative extinction of the entire helium droplet upon capture of particles. It is shown that the attenuation of the He droplet beam in the process of the cluster growth can be used in order to obtain the average size and the binding energy of the clusters. Furthermore, we used He droplets for assembling and surface deposition of gold and silver clusters having about 500 atoms. Typical deposition rate of metal atoms of about 3 x 10(15) atoms sr(-1) s(-1) is comparable to or larger than obtained with other beam deposition techniques. We propose that doping of He droplets by Au and Ag atoms in two separate pickup chambers leads to formation of the bimetal clusters having core-shell structure.
Collapse
Affiliation(s)
- Vadim Mozhayskiy
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | | | | | | |
Collapse
|
46
|
Döppner T, Diederich T, Göde S, Przystawik A, Tiggesbäumker J, Meiwes-Broer KH. Ion induced snowballs as a diagnostic tool to investigate the caging of metal clusters in large helium droplets. J Chem Phys 2007; 126:244513. [PMID: 17614570 DOI: 10.1063/1.2745294] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Metal clusters embedded in ultracold helium nanodroplets are exposed to femtosecond laser pulses with intensities of 10(13)-10(14) W/cm2. The influence of the matrix on the ionization and fragmentation dynamics is studied by pump-probe time-of-flight mass spectrometry. Special attention is paid to the generation of helium snowballs around positive metal ions (Me(z+)He(N), z=1,2). Closings of the first and second helium shells are found for silver at N(1)=10,12 and N(2)=32,44, as well as for magnesium at N1=19-20. The distinct abundance enhancement of helium snowballs in the presence of isolated atoms and small clusters in the droplets is used as a diagnostics to explore the cage effect. For silver, a reaggregation of the clusters is observed at 30 ps after femtosecond laser excitation.
Collapse
Affiliation(s)
- Tilo Döppner
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | | | | | | | | | | |
Collapse
|
47
|
Loginov E, Drabbels M. Excited State Dynamics of Ag Atoms in Helium Nanodroplets. J Phys Chem A 2007; 111:7504-15. [PMID: 17569515 DOI: 10.1021/jp0716278] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The excited state dynamics of silver atoms embedded in helium nanodroplets have been investigated by a variety of spectroscopic techniques. The experiments reveal that 5p 2P1/2 <-- 5s 2S1/2 excitation of embedded silver atoms results almost exclusively in the ejection of silver atoms populating the 2P1/2 state. In contrast, excitation to the 5p 2P3/2 state leads to the ejection of not only silver atoms in the 2P1/2, 2P3/2, and 2D5/2 excited states but also of AgHe and AgHe2. These AgHe exciplexes are mainly formed in the A2Pi1/2 electronic state. In addition, it is found that a considerable fraction of the 2P3/2 excited silver atoms become solvated within the helium droplets, most probably as AgHe2. The observations can be accounted for by a model in which the metastable 2D5/2 state of silver acts as a doorway state in the relaxation of 2P3/2 excited silver atoms.
Collapse
Affiliation(s)
- Evgeniy Loginov
- Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédéral de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | |
Collapse
|
48
|
Przystawik A, Radcliffe P, Diederich T, Döppner T, Tiggesbäumker J, Meiwes-Broer KH. Photoelectron studies of neutral Ag3 in helium droplets. J Chem Phys 2007; 126:184306. [PMID: 17508802 DOI: 10.1063/1.2723087] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Photoelectron spectra of neutral silver trimers, grown in ultracold helium nanodroplets, are recorded after ionization with laser pulses via a strong optical resonance of this species. Varying the photon energy reveals that direct vertical two-photon ionization is hindered by a rapid relaxation into the lower edge of a long-living excited state manifold. An analysis of the ionization threshold of the embedded trimer yields an ionization potential of 5.74+/-0.09 eV consistent with the value found in the gas phase. The asymmetrical form of the electron energy spectrum, which is broadened toward lower kinetic energies, is attributed to the influence of the matrix on the photoionization process. The lifetime of the excited state was measured in a two-color pump-probe experiment to be 5.7+/-0.6 ns.
Collapse
|
49
|
Fárník M, Toennies JP. Ion-molecule reactions in 4He droplets: flying nano-cryo-reactors. J Chem Phys 2007; 122:14307. [PMID: 15638659 DOI: 10.1063/1.1815272] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ion-molecule reactions are studied inside large (approximately equal to 10(4) atoms) very cold (0.37 K) superfluid (4)He droplets by mass spectrometric detection of the product ions. He+ ions initially formed inside the droplets by electron impact ionization undergo charge transfer with either embedded D(2), N(2), or CH(4). For D(2) this charge transfer process was studied in detail by varying the pickup pressure. For either N(2) or CH(4) the reagent ions were formed by this charge transfer and the reaction pathways of the secondary reactions N(2) (+)+D(2), CH(4) (+)+D(2), and CH(3) (+)+D(2) each with an additionally embedded D(2) molecule were also determined from the pickup pressure dependencies. In several cases, notably He.N(2) (+) and CH(3)D(2) (+) reaction intermediates are observed. The analysis is facilitated by the tendency for molecular ion products to appear without (or with only very few) attached He atoms whereas the atomic ion products usually appear in the mass spectra with several attached He atoms, e.g., He(m).D+ ions with up to m=19.
Collapse
Affiliation(s)
- Michal Fárník
- Max-Planck Institut für Strömungsforschung, Bunsenstrasse 10, D-37073 Göttingen, Germany.
| | | |
Collapse
|
50
|
Cargnoni F, Mella M, Raimondi M. Application of valence-bond techniques to the study of weakly bound complexes. The potential energy surface of the Ne–CH4system. Phys Chem Chem Phys 2007; 9:2457-69. [PMID: 17508080 DOI: 10.1039/b700143f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a comprehensive survey of the Molecular Orbital-Valence Bond (MO-VB) method, a theoretical scheme developed within the framework of the Valence Bond theory to deal with weakly bound intermolecular complexes. According to the MO-VB, the wavefunction of the system is expressed as a truncated non-orthogonal Configuration Interaction expansion, which is size extensive and a priori free of basis set superposition error. We report on the recent developments of the method, which extend the range of application of the MO-VB to intermolecular complexes with a quite large number of correlated electrons, showing that VB-based methods are nowadays a valid alternative to Molecular Orbital approaches also in this field. The MO-VB has been applied to study extensively the Ne-CH(4) complex, and compared with the more standard MP4 and CCSD(T) results. We determined two analytical Potential Energy Surfaces (PES) for this system, computed at MO-VB and MP4 level, which represent the first ones coming entirely from ab initio computations. The features of our potentials are discussed, and compared to the single analytical potential which includes the anisotropy available in the literature, determined about twenty years ago by Udo Buck and co-workers using a semiempirical approach [U. Buck, A. Kolhase, D. Secrest, T. Phillips, G. Scoles and F. Grein, Mol. Phys., 1985, 55, 1233]. The differences among the three PES are quite relevant, and are due to play a relevant role in the theoretical simulations of the dynamical properties of the Ne-CH(4) system.
Collapse
Affiliation(s)
- F Cargnoni
- ISTM-CNR, Via Golgi 19, 20133 Milano, Italy.
| | | | | |
Collapse
|