Velocity map imaging study of OCS photodissociation followed by S(1S) autoionization at 157 nm |
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| Authors: | Shiou-Min Wu Xueming Yang David H Parker |
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| Institution: | 1. Department of Molecular and Laser Physics, Institute for Molecules and Materials , Radboud University Nijmegen , Nijmegen , NL-6500 GL , The Netherlands;2. State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian, Liaoning , 116023 , People's Republic of China |
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| Abstract: | Atomic sulphur ions (S+) were observed directly by crossing a carbonyl sulphide (OCS) molecular beam with a F2 laser. In this study both S+ ion and electron images were measured using the velocity map imaging technique. The results imply that S+ is produced from the well-known photodissociation of OCS at 157 nm leading to the dominant S(1S) + CO(1Σ+) channel, and then the excited S(1S) atom is directly ionized by another 157 nm photon. Correlated vibrationally resolved angular distributions and internal energy distribution of the CO coproducts are reported here and compared with previous studies. This experiment yields strong and sharp S+ images which may be useful for calibrating any imaging or laser ionization apparatus when using a 157 nm laser. A number of technical aspects such as corrections for partial slicing and imperfect laser polarization are described. Abstraction of product angular distributions using both polarized and unpolarized photolysis lasers is also demonstrated using velocity map imaging. |
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