The rate coefficients for the reactions of Ar+and Ar+2with CH4and CS2are obtained as a function of energy by using a selected ion flow tube with an electric drift field (SIFThyphen;DRIFT). A diagnostic analysis of the system and technique has been completed and allows rate coefficients to be reported with a high level of confidence. Rate coefficients and product branching ratios are determined for the methane reactions from thermal (room temperature) to centerhyphen;ofhyphen;mass kinetic energies of about 0.15 eV and for the carbon disulfide reactions from thermal to about 0.6 eV. The overall rate coefficients for these reactions do not vary a great deal over the investigated energy range. The greatest dependence is found for the slowest reaction Ar+with CS2, where a minimum in the rate coefficient is observed near 0.15 eV. The behavior of the branching ratios for S+and CS+2suggests curve crossings between a repulsive state and theA,B, andCelectronic states of CS+2.
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