ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We have measured rate coefficients and product branching ratios for the reactions of labeled and unlabeled sulfur anions with CS2, OCS, and H2S. These studies were carried out as a function of kinetic energy in the range between 298 K and ∼1 eV using a tandem flowing afterglow-selected ion flow drift tube instrument. For the reaction of S−+CS2 as a function of increasing kinetic energy, the total rate coefficient initially decreases, reaches a minimum at about 0.4 eV, and then increases. Thermoneutral isotope exchange is responsible for the negative energy dependence at lower energies and endothermic sulfur abstraction is responsible for the positive energy dependence at higher energies. For the reaction of S−+OCS vs kinetic energy, the total rate coefficient initially decreases, reaches a plateau, and then increases slightly. Thermoneutral isotope exchange and exothermic sulfur atom abstraction are responsible for the negative energy dependence. For the reaction of S−+H2S, the total rate coefficient has a very weak energy dependence. The strong negative energy dependence of the thermoneutral isotope exchange is counterbalanced by the positive energy dependence of the slightly endothermic hydrogen and proton transfer channels. For these reactions isotope exchange may proceed by formation of an intermediate collision complex, whereas sulfur abstraction may proceed by two different mechanisms, complex formation at lower energies and direct attack on sulfur at higher energies. © 1994 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.467982
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