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Gianturco FA, Lakhmanskaya OY, Vera MH, Yurtsever E, Wester R. Collisional relaxation kinetics for ortho and para NH 2- under photodetachment in cold ion traps. Faraday Discuss 2018; 212:117-135. [PMID: 30234217 DOI: 10.1039/c8fd00078f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The collisional cooling of the internal rotational states of the nonlinear anion NH2- (1A1), occurring at the low temperature of a cold ion trap under helium buffer gas cooling, is examined via quantum dynamics calculations and ion decay rate measurements. The calculations employ a novel ab initio potential energy surface that describes the interaction anisotropy and range of action between the molecular anions and the neutral He atoms. The state changing integral cross sections are employed to obtain the state-to-state rate coefficients, separately for the ortho- and the para-NH2- ions. These rates are in turn used to compute the state population evolution in the trap for both species, once photodetachment by a laser is initiated in the trap. The present work shows results for the combined losses of both species after the photodetachment laser is switched on and analyzes the differences of loss kinetics between the two hyperfine isomers.
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Affiliation(s)
- Francesco A Gianturco
- Institut für Ionenphysik und Angewandte Physik Universität Innsbruck, Technikerstraße 25/3, A-6020 Innsbruck, Austria.
| | - Olga Y Lakhmanskaya
- Institut für Ionenphysik und Angewandte Physik Universität Innsbruck, Technikerstraße 25/3, A-6020 Innsbruck, Austria.
| | - Mario Hernández Vera
- Institut für Ionenphysik und Angewandte Physik Universität Innsbruck, Technikerstraße 25/3, A-6020 Innsbruck, Austria. and Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 7 (C), D-81377 München, Germany
| | - Ersin Yurtsever
- Department of Chemistry, Koç University, TR-34450, Istanbul, Turkey
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik Universität Innsbruck, Technikerstraße 25/3, A-6020 Innsbruck, Austria.
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Hernández Vera M, Yurtsever E, Wester R, Gianturco FA. NH 2- in a cold ion trap with He buffer gas: Ab initio quantum modeling of the interaction potential and of state-changing multichannel dynamics. J Chem Phys 2018; 148:184305. [PMID: 29764131 DOI: 10.1063/1.5022633] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present an extensive range of accurate ab initio calculations, which map in detail the spatial electronic potential energy surface that describes the interaction between the molecular anion NH2- (1A1) in its ground electronic state and the He atom. The time-independent close-coupling method is employed to generate the corresponding rotationally inelastic cross sections, and then the state-changing rates over a range of temperatures from 10 to 30 K, which is expected to realistically represent the experimental trapping conditions for this ion in a radio frequency ion trap filled with helium buffer gas. The overall evolutionary kinetics of the rotational level population involving the molecular anion in the cold trap is also modelled during a photodetachment experiment and analyzed using the computed rates. The present results clearly indicate the possibility of selectively detecting differences in behavior between the ortho- and para-anions undergoing photodetachment in the trap.
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Affiliation(s)
- Mario Hernández Vera
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Ersin Yurtsever
- Department of Chemistry, Koç University, Rumelifeneriyolu, Sariyer TR-34450, Istanbul, Turkey
| | - Roland Wester
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
| | - Franco A Gianturco
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria
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Sarma G, Saha AK, Bishwakarma CK, Scheidsbach R, Yang CH, Parker D, Wiesenfeld L, Buck U, Mavridis L, Marinakis S. Collision energy dependence of state-to-state differential cross sections for rotationally inelastic scattering of H 2O by He. Phys Chem Chem Phys 2017; 19:4678-4687. [PMID: 28127600 DOI: 10.1039/c6cp06495g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The inelastic scattering of H2O by He as a function of collision energy in the range 381 cm-1 to 763 cm-1 at an energy interval of approximately 100 cm-1 has been investigated in a crossed beam experiment using velocity map imaging. Change in collision energy was achieved by varying the collision angle between the H2O and He beam. We measured the state-to-state differential cross section (DCS) of scattered H2O products for the final rotational states JKaKc = 110, 111, 221 and 414. Rotational excitation of H2O is probed by (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectroscopy. DCS measurements over a wide range of collision energies allowed us to probe the H2O-He potential energy surface (PES) with greater detail than in previous work. We found that a classical approximation of rotational rainbows can predict the collision energy dependence of the DCS. Close-coupling quantum mechanical calculations were used to produce DCS and partial cross sections. The forward-backward ratio (FBR), is introduced here to compare the experimental and theoretical DCS. Both theory and experiments suggest that an increase in the collision energy is accompanied with more forward scattering.
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Affiliation(s)
- Gautam Sarma
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | - Ashim Kumar Saha
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | | | - Roy Scheidsbach
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | - Chung-Hsin Yang
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
| | - David Parker
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands
| | | | - Udo Buck
- Max-Planck-Institut für Dynamik und Selbst-Organisation, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Lazaros Mavridis
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, Joseph Priestley Building, Mile End Road, London, E1 4NS, UK.
| | - Sarantos Marinakis
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, Joseph Priestley Building, Mile End Road, London, E1 4NS, UK.
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Dagdigian PJ, Alexander MH. Exact quantum scattering calculations of transport properties for the H2O–H system. J Chem Phys 2013; 139:194309. [DOI: 10.1063/1.4829681] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Tscherbul TV, Grinev TA, Yu HG, Dalgarno A, Kłos J, Alexander MH. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH 2(X̃) collisions. J Chem Phys 2012; 137:104302. [DOI: 10.1063/1.4748258] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Gubbels KB, Ma Q, Alexander MH, Dagdigian PJ, Tanis D, Groenenboom GC, van der Avoird A, van de Meerakker SYT. Resonances in rotationally inelastic scattering of OH(X2Π) with helium and neon. J Chem Phys 2012; 136:144308. [PMID: 22502519 DOI: 10.1063/1.3697816] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH (X(2)Π, j = 3/2, F(1), f) radicals with He and Ne atoms. We calculate new ab initio potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare well with the recent crossed beam scattering experiment of Kirste et al. [Phys. Rev. A 82, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.
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Affiliation(s)
- Koos B Gubbels
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
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Dagdigian PJ, Alexander MH. Theoretical investigation of rotationally inelastic collisions of CH2(X̃) with helium. J Chem Phys 2012; 136:224306. [DOI: 10.1063/1.4729050] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Paterson G, Costen ML, McKendrick KG. Collisional depolarisation of rotational angular momentum: influence of the potential energy surface on the collision dynamics? INT REV PHYS CHEM 2012. [DOI: 10.1080/0144235x.2012.659046] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Paterson G, Relf A, Costen ML, McKendrick KG, Alexander MH, Dagdigian PJ. Rotationally elastic and inelastic dynamics of NO(X2Π, v = 0) in collisions with Ar. J Chem Phys 2011; 135:234304. [PMID: 22191872 DOI: 10.1063/1.3665135] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A combined theoretical and experimental study of the depolarization of selected NO(X(2)Π, v = 0, j, F, ɛ) levels in collisions with a thermal bath of Ar has been carried out. Rate constants for elastic depolarization of rank K = 1 (orientation) and K = 2 (alignment) were extracted from collision-energy-dependent quantum scattering calculations, along with those for inelastic population transfer to discrete product levels. The rate constants for total loss of polarization of selected initial levels, which are the sum of elastic depolarization and population transfer contributions, were measured using a two-color polarization spectroscopy technique. Theory and experiment agree qualitatively that the rate constants for total loss of polarization decline modestly with j, but the absolute values differ by significantly more than the statistical uncertainties in the measurements. The reasons for this discrepancy are as yet unclear. The lack of a significant K dependence in the experimental data is, however, consistent with the theoretical prediction that elastic depolarization makes only a modest contribution to the total loss of polarization. This supports a previous conclusion that elastic depolarization for NO(X(2)Π) + Ar is significantly less efficient than for the electronically closely related system OH(X(2)Π) + Ar [P. J. Dagdigian and M. H. Alexander, J. Chem. Phys. 130, 204304 (2009)].
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Affiliation(s)
- G Paterson
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
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Dagdigian PJ, Alexander MH. Theoretical investigation of rotationally inelastic collisions of the methyl radical with helium. J Chem Phys 2011; 135:064306. [DOI: 10.1063/1.3624525] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ma L, Alexander MH, Dagdigian PJ. Theoretical investigation of rotationally inelastic collisions of CH2(ã) with helium. J Chem Phys 2011; 134:154307. [DOI: 10.1063/1.3575200] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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