| Autor: |
Alligood, Bridget W., FitzPatrick, Benjamin L., Glassman, Emily Jane, Butler, Laurie J., Kai-Chung Lau |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 7/28/2009, Vol. 131 Issue 4, p044305, 14p, 1 Diagram, 2 Charts, 11 Graphs |
| Abstrakt: |
The dissociation dynamics of methylsulfonyl radicals generated from the photodissociation of CH3SO2Cl at 193 nm is investigated by measuring product velocities in a crossed laser-molecular beam scattering apparatus. The data evidence three primary photodissociation channels of the precursor: S–Cl fission to produce Cl atoms and ground electronic state CH3SO2 radicals, S–Cl fission to produce Cl atoms and electronically excited CH3SO2 radicals, and S–CH3 fission. Some of the vibrationally excited CH3SO2 radicals undergo subsequent dissociation to CH3+SO2, as do all of the electronically excited radicals. The velocities of the SO2 products show that the vibrationally excited ground state CH3SO2 radicals dissociate via a loose transition state having a small exit barrier beyond the endoergicity. Hence, a statistical recoil kinetic energy distribution should and does fit the distribution of velocities imparted to these SO2 products. The electronically excited CH3SO2 radicals also dissociate to CH3+SO2, but with a larger average release to relative kinetic energy. Interestingly, when using 200 eV electron bombardment detection, the ground electronic state CH3SO2 radicals having too little internal energy to dissociate are not observed at the parent CH3SO2+ ion, but only at the CH3+ daughter ion. They are distinguished by virtue of the velocity imparted in the original photolytic step; the detected velocities of the stable radicals are consistent with the calculated barrier of 14.6 kcal/mol for the dissociation of CH3SO2 to CH3+SO2. We present CCSD(T) calculations of the adiabatic excitation energy to the lowest excited state of CH3SO2 radicals, the 1 2A″ state, as well as the vertical energy from the equilibrium geometry of that excited state to the 2 2A″ state, to aid in the experimental assignment. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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