標題: Dissociation of energy-selected c-C2H4S+ in a region 10.6-11.8 eV: Threshold photoelectron-photoion coincidence experiments and quantum-chemical calculations
作者: Fang, YS
Lin, IF
Lee, YC
Chiang, SY
應用化學系
Department of Applied Chemistry
公開日期: 1-八月-2005
摘要: Dissociation of energy-selected c-C2H4S+ was investigated in a region of 10.6-11.8 eV with a threshold photoelectron-photoion coincidence technique and a synchrotron as a source of vacuum ultraviolet radiation. Branching ratios and average releases of kinetic energy in channels of formation of c-C2H4S+, CH3CS+, and HCS+ were obtained from well-resolved time-of-flight peaks in coincidence mass spectra. Measured average releases of kinetic energy for channel CH3CS++H of least energy are substantial and much greater than calculated with quasiequilibrium theory; in contrast, small releases of kinetic energy near the appearance onset for channel HCS++CH3 agree satisfactorily with statistical calculations. Calculations of molecular electronic structures and energetics of c-C2H4S+ and C2H3S+ isomers and various fragments and transition states were also performed with Gaussian 3 method to establish dissociation mechanisms. A predicted dissociation energy of 11.05 eV for c-C2H4S -> HCS++CH3 agrees with a linearly extrapolated threshold at 10.99 +/- 0.04 eV and a predicted dissociation mechanism that c-C2H4S+ isomerizes to CH3CHS+ before dissociating to HCS++CH3 supports the experimental results. The large releases of kinetic energy for channel CH3CS++H might result from a dissociation mechanism according to which c-C2H4S+ isomerizes to a local minimum CH3CSH+ and then dissociates through a transition state to form CH3CS++H. (C) 2005 American Institute of Physics.
URI: http://dx.doi.org/10.1063/1.1993589
http://hdl.handle.net/11536/13454
ISSN: 0021-9606
DOI: 10.1063/1.1993589
期刊: JOURNAL OF CHEMICAL PHYSICS
Volume: 123
Issue: 5
結束頁: 
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