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Schatz GC, Wodtke AM, Yang X. Spiers Memorial Lecture: New directions in molecular scattering. Faraday Discuss 2024. [PMID: 38764350 DOI: 10.1039/d4fd00015c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2024]
Abstract
The field of molecular scattering is reviewed as it pertains to gas-gas as well as gas-surface chemical reaction dynamics. We emphasize the importance of collaboration of experiment and theory, from which new directions of research are being pursued on increasingly complex problems. We review both experimental and theoretical advances that provide the modern toolbox available to molecular-scattering studies. We distinguish between two classes of work. The first involves simple systems and uses experiment to validate theory so that from the validated theory, one may learn far more than could ever be measured in the laboratory. The second class involves problems of great complexity that would be difficult or impossible to understand without a partnership of experiment and theory. Key topics covered in this review include crossed-beams reactive scattering and scattering at extremely low energies, where quantum effects dominate. They also include scattering from surfaces, reactive scattering and kinetics at surfaces, and scattering work done at liquid surfaces. The review closes with thoughts on future promising directions of research.
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Affiliation(s)
- George C Schatz
- Dept of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Alec M Wodtke
- Institute for Physical Chemistry, Georg August University, Goettingen, Germany
- Max Planck Institute for Multidisciplinary Natural Sciences, Goettingen, Germany.
- International Center for the Advanced Studies of Energy Conversion, Georg August University, Goettingen, Germany
| | - Xueming Yang
- Dalian Institute for Chemical Physics, Chinese Academy of Sciences, Dalian, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen, China
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2
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Plomp V, Wang XD, Kłos J, Dagdigian PJ, Lique F, Onvlee J, van de Meerakker SY. Imaging Resonance Effects in C + H 2 Collisions Using a Zeeman Decelerator. J Phys Chem Lett 2024; 15:4602-4611. [PMID: 38640083 PMCID: PMC11071073 DOI: 10.1021/acs.jpclett.3c03379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 04/05/2024] [Accepted: 04/05/2024] [Indexed: 04/21/2024]
Abstract
An intriguing phenomenon in molecular collisions is the occurrence of scattering resonances, which originate from bound and quasi-bound states supported by the interaction potential at low collision energies. The resonance effects in the scattering behavior are extraordinarily sensitive to the interaction potential, and their observation provides one of the most stringent tests for theoretical models. We present high-resolution measurements of state-resolved angular scattering distributions for inelastic collisions between Zeeman-decelerated C(3P1) atoms and para-H2 molecules at collision energies ranging from 77 cm-1 down to 0.5 cm-1. Rapid variations in the angular distributions were observed, which can be attributed to the consecutive reduction of contributing partial waves and effects of scattering resonances. The measurements showed excellent agreement with distributions predicted by ab initio quantum scattering calculations. However, discrepancies were found at specific collision energies, which most likely originate from an incorrectly predicted quasi-bound state. These observations provide exciting prospects for further high-precision and low-energy investigations of scattering processes that involve paramagnetic species.
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Affiliation(s)
- Vikram Plomp
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Xu-Dong Wang
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jacek Kłos
- University
of Maryland, Department of Physics,
Joint Quantum Institute, College
Park, Maryland 20742, United States of America
| | - Paul J. Dagdigian
- Johns
Hopkins University, Department of Chemistry, Baltimore, Maryland 21218, United States
of America
| | - François Lique
- Université
de Rennes, Institut de Physique
de Rennes, 263 avenue
du Général Leclerc, Rennes CEDEX 35042, France
| | - Jolijn Onvlee
- Radboud
University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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3
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Plomp V, Onvlee J, Lique F, van de Meerakker SYT. Low-Energy Collisions of Zeeman-Decelerated NH Radicals with He Atoms. J Phys Chem A 2023; 127:2306-2313. [PMID: 36884215 PMCID: PMC10026067 DOI: 10.1021/acs.jpca.2c08712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
We report an experimental study of state-to-state inelastic scattering of NH (X 3Σ-, N = 0, j = 1) radicals with He atoms. Using a crossed molecular beam apparatus that combines a Zeeman decelerator and velocity map imaging, we study both integral and differential cross sections in the N = 0, j = 1 → N = 2, j = 3 inelastic channel. We developed various new REMPI schemes to state-selectively detect NH radicals, and tested their performance in terms of sensitivity and ion recoil velocity. We found a 1 + 2' + 1' REMPI scheme using the A 3Π ← X 3Σ- resonant transition, which yields acceptable recoil velocities and is more than an order of magnitude more sensitive than conventional one-color REMPI schemes to detect NH. We used this REMPI scheme to probe state-to-state integral and differential cross sections around the channel opening at 97.7 cm-1, as well as at higher energies where structure in the scattering images could be resolved. The experimental results are in excellent agreement with the predictions from quantum scattering calculations which are based on an ab initio NH-He potential energy surface.
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Affiliation(s)
- Vikram Plomp
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jolijn Onvlee
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - François Lique
- Institut de Physique de Rennes, Université de Rennes 1, 263 avenue du Général Leclerc, 35042 Rennes CEDEX, France
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4
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Chien TE, Hohmann L, Harding DJ. Near-ambient pressure velocity map imaging. J Chem Phys 2022; 157:034201. [DOI: 10.1063/5.0098495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We present a new velocity map imaging instrument for studying molecular beam surface scattering in a near-ambient pressure (NAP-VMI) environment. The instrument offers the possibility to study chemical reaction dynamics and kinetics where higher pressures are either desired or unavoidable, adding a new tool to help close the “pressure gap” between surface science and applied catalysis. NAP-VMI conditions are created by two sets of ion optics that guide ions through an aperture and map their velocities. The aperture separates the high pressure ionization region and maintains the necessary vacuum in the detector region. The performance of the NAP-VMI is demonstrated with results from N2O photodissociation and N2 scattering from a Pd(110) surface, which are compared under vacuum and at near-ambient pressure (1 × 10−3 mbar). NAP-VMI has the potential to be applied to, and useful for, a broader range of experiments, including photoelectron spectroscopy and scattering with liquid microjets.
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Affiliation(s)
- Tzu-En Chien
- Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm 100 44, Sweden
| | - Lea Hohmann
- Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm 100 44, Sweden
| | - Dan J. Harding
- Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm 100 44, Sweden
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5
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Tang G, Besemer M, Onvlee J, Karman T, van der Avoird A, Groenenboom GC, van de Meerakker SYT. Correlated rotational excitations in NO–CO inelastic collisions. J Chem Phys 2022; 156:214304. [DOI: 10.1063/5.0092561] [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
We present a joint experimental and theoretical study of rotationally inelastic collisions between NO ( X2Π1/2, ν = 0, j = 1/2, f) radicals and CO ( X1Σ+, ν = 0, j = 0) molecules at a collision energy of 220 cm−1. State-to-state scattering images for excitation of NO radicals into various final states were measured with high resolution by combining the Stark deceleration and velocity map imaging techniques. The high image resolution afforded the observation of correlated rotational excitations of NO–CO pairs, which revealed a number of striking scattering phenomena. The so-called “parity-pair” transitions in NO are found to have similar differential cross sections, independent of the concurrent excitation of CO, extending this well-known effect for collisions between NO and rare gas atoms into the realm of bimolecular collisions. Forward scattering is found for collisions that induce a large amount of rotational energy transfer (in either NO, CO, or both), which require low impact parameters to induce sufficient energy transfer. This observation is interpreted in terms of the recently discovered hard collision glory scattering mechanism, which predicts the forward bending of initially backward receding trajectories if the energy uptake in the collision is substantial in relation to the collision energy. The experimental results are in good agreement with the predictions from coupled-channels quantum scattering calculations based on an ab initio NO–CO potential energy surface.
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Affiliation(s)
- Guoqiang Tang
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Matthieu Besemer
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jolijn Onvlee
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Tijs Karman
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ad van der Avoird
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Gerrit C. Groenenboom
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Mapping partial wave dynamics in scattering resonances by rotational de-excitation collisions. Nat Chem 2022; 14:538-544. [PMID: 35210587 DOI: 10.1038/s41557-022-00896-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 01/21/2022] [Indexed: 11/09/2022]
Abstract
One of the most important parameters in a collision is the 'miss distance' or impact parameter, which in quantum mechanics is described by quantized partial waves. Usually, the collision outcome is the result of unavoidable averaging over many partial waves. Here we present a study of low-energy NO-He collisions that enables us to probe how individual partial waves evolve during the collision. By tuning the collision energies to scattering resonances between 0.4 and 6 cm-1, the initial conditions are characterized by a limited set of partial waves. By preparing NO in a rotationally excited state before the collision and by studying rotational de-excitation collisions, we were able to add one quantum of angular momentum to the system and trace how it evolves. Distinct fingerprints in the differential cross-sections yield a comprehensive picture of the partial wave dynamics during the scattering process. Exploiting the principle of detailed balance, we show that rotational de-excitation collisions probe time-reversed excitation processes with superior energy and angular resolution.
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Plomp V, Wang XD, Lique F, Kłos J, Onvlee J, van de Meerakker SYT. High-Resolution Imaging of C + He Collisions using Zeeman Deceleration and Vacuum-Ultraviolet Detection. J Phys Chem Lett 2021; 12:12210-12217. [PMID: 34928163 PMCID: PMC8724800 DOI: 10.1021/acs.jpclett.1c03643] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/13/2021] [Indexed: 05/25/2023]
Abstract
High-resolution measurements of angular scattering distributions provide a sensitive test for theoretical descriptions of collision processes. Crossed beam experiments employing a decelerator and velocity map imaging have proven successful to probe collision cross sections with extraordinary resolution. However, a prerequisite to exploit these possibilities is the availability of a near-threshold state-selective ionization scheme to detect the collision products, which for many species is either absent or inefficient. We present the first implementation of recoil-free vacuum ultraviolet (VUV) based detection in scattering experiments involving a decelerator and velocity map imaging. This allowed for high-resolution measurements of state-resolved angular scattering distributions for inelastic collisions between Zeeman-decelerated carbon C(3P1) atoms and helium atoms. We fully resolved diffraction oscillations in the angular distributions, which showed excellent agreement with the distributions predicted by quantum scattering calculations. Our approach offers exciting prospects to investigate a large range of scattering processes with unprecedented precision.
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Affiliation(s)
- Vikram Plomp
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Xu-Dong Wang
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - François Lique
- Université
de Rennes, Institut de Physique de Rennes, 263 avenue du Général
Leclerc, Rennes 35042 CEDEX, France
| | - Jacek Kłos
- University
of Maryland, Department of Physics, Joint
Quantum Institute, College Park, Maryland 20742, United States of America
| | - Jolijn Onvlee
- Radboud
University, Institute for Molecules and
Materials, Heijendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
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