Product Branching Fractions Research Articles

Reactive quenching studies of Xe (6s, 3P2) metastable atoms by chlorine containing molecules

The XeCl* emission spectrum has been used to study the reactions of Xe (6s, 3P2) metastable atoms with 20 chlorine containing reagents. Although the total quenching rate constants are large, only Cl2, the mixed halogens and Group VI chlorides have high product branching fractions for XeCl* excimer formation. From analysis of the low pressure XeCl* emission spectra, the ratios for XeCl (III,1/2 or B,1/2) and XeCl (II,3/2 or C,3/2) formation were determined. Using results presented in the following paper, the vibrational energy distributions of the XeCl* molecules also can be estimated. A wide difference, depending upon reagent, is observed for the vibrational energy disposal. The short wavelength limit of the XeCl (B–X) emission can be used to assign upper limits to D°0 (R–Cl) and this work gives D°0 (SCl–Dl) ?44.7; D°0 (ClS2–Cl) ?46.2, D°0 (SOCl–Cl) ?53.9; D°0 (SO2–Cl) ?58.5, and D°0 (PCl2–Cl) ?77.7 kcal mole−1. For purposes of comparison, the XeCl* emission spectra also were obtained from the reaction of Xe (6s, 3P1) resonance atoms with Cl2, PCl2, CCl4, and COCl2. The branching ratios and energy disposal for Xe ( 3P2) and Xe ( 3P1) reactions appear to be qualitatively similar. Based upon all of these data, the dynamics of the reactions between Xe ( 3P2) and the chlorine containing reagents are discussed and compared to the models in the literature used previously for the reactions of alkali metal atoms with halogen containing molecules. Characteristic XeI* and XeBr* spectra from Xe ( 3P2) atom reactions are included in an Appendix.