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Wang P, Lin Q, Xiao C, Yang X, Liu K, Pan H. Unraveling the Photodissociation Branching and Pathways of Methane at 118 nm by Imaging the CH 3, CH 2, and CH Fragments. J Phys Chem A 2024; 128:5273-5284. [PMID: 38946501 DOI: 10.1021/acs.jpca.4c01914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Under irradiation of a vacuum ultraviolet (VUV) photon, methane dissociates and yields multiple fragments. This photochemical behavior is not only of fundamental importance but also with wide-ranging implications in several branches of science. Despite that and numerous previous investigations, the product channel branching is still under debate, and the underlying dissociation mechanisms remain elusive. In this study, the photofragment imaging technique was exploited for the first time to map out the momentum and anisotropy parameter distributions of the CH3, CH2, and CH fragments at the 118 nm photolysis wavelength (10.48 eV photon energy). In conjunction with previously reported results of the H atom fragment at 121.6 nm (10.2 eV), a complete set of product channel branching in both two-body and three-body fragmentations is accurately determined. We concluded that extensive nonadiabatic transitions partake in the processes with two-body fragmentations accounting for more than 90% of overall photodissociation, for which the channel branching values for CH2 + H2 and CH3 + H are about 0.66 and 0.25, respectively. Careful kinematic analysis enables us to untangle the intertwined triple fragmentations into the CH2(X̃ 3B1 and ã 1A1) + H + H and CH(X2Π) + H + H2 channels and to evidence their underlying sequential (or stepwise) mechanisms. With the aid of electronic correlation and prior theoretical calculations of the potential energy surfaces, the most probable or dominant dissociation pathways are elucidated. Comparisons with fragmentary reports in the literature on various photochemical aspects are also documented, and discrepancies are clarified. This comprehensive study benchmarks the VUV photochemistry of methane and advances our understanding of this important process.
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Affiliation(s)
- Pengcheng Wang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Qiaosong Lin
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Chunlei Xiao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Kopin Liu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
- Aerosol Science Research Center, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, Taipei 10617, Taiwan
| | - Huilin Pan
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, CAS, Dalian 116023, P. R. China
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, P. R. China
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Thissen R, Vuitton V, Lavvas P, Lemaire J, Dehon C, Dutuit O, Smith MA, Turchini S, Catone D, Yelle RV, Pernot P, Somogyi A, Coreno M. Laboratory Studies of Molecular Growth in the Titan Ionosphere. J Phys Chem A 2009; 113:11211-20. [DOI: 10.1021/jp9050353] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Roland Thissen
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Veronique Vuitton
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Panayotis Lavvas
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Joel Lemaire
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Christophe Dehon
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Odile Dutuit
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Mark A. Smith
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Stefano Turchini
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Daniele Catone
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Roger V. Yelle
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Pascal Pernot
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Arpad Somogyi
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
| | - Marcello Coreno
- Laboratoire de Planétologie de Grenoble, CNRS, Université J. Fourier, UMR 5109, Grenoble, France, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, Laboratoire de Chimie Physique, CNRS, Université Paris-Sud, UMR 8000, Orsay, France, Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, CNR-ISM, Roma, Italy, and CNR-IMIP & INFM-TASC, Elettra Sincrotrone, Trieste, Italy
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