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

Abstract

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.

Optimization of a Dielectric Barrier Discharge for Pulsed UV Emission of XeCl at 308 nm

“…HCl has large cross sections for dissociative electron attachment [33] that produces chlorine ions and supports reactions 2 and 3. Cl 2 is a favourable donor in case of the harpoon reaction 1 because then XeCl is the main quenching product of metastable xenon atoms by Cl 2 in contrast to other chlorine containing molecules [34][35][36]. To clarify this question in our experimental condition, we will consider our measured decay times in more detail.…”

Chemiluminescence polarization measurements under supersonic beam-gas conditions

“…The reaction is endoergic by approximately 13 kJ tool-i j; the crosssection remains small even well above threshold and the branching ratio into the atom transfer channel is only 2 per cent [12]. In consequence, it is virtually impossible to study the reaction under crossed-beam conditions, and the adoption of the beam-gas configuration becomes essential.…”

Molecular dynamics of metastable atomic reactions: translational energy threshold and product rotational alignment in the reaction of Xe(3P2,0) with CH3Br

“…If this were the only significant parameter, however, the threshold energies for Br-transfer would be independent of the attacking atom, contrary to observation. The differences could arise through pre-stretching [8,24] associated with reagent interactions outside the vertical electron jump distance. This effect, which would reduce the negative electron affinity, would be most pronounced at low reagent velocities and would favour the heavier attacking atoms at any given collision energy.…”

“…Measurements of translational excitation functions and of product rotational alignment at centre of mass collision energies in the range 10-125 kJ mo1-1 [1] complement the wealth of information gathered at thermal collision energies, principally by Setser and his co-workers [5][6][7][8][9] on vibrational energy disposal, product branching ratios and absolute cross-sections. The new measurements show that the analogy between alkali metal and metastable atomic rare gas reactions [5] continues to operate at elevated collision energies [4].…”