Speed and angular relaxation processes induced by collisions with He, Ar, Ne, Xe, N2, and O2 for the velocity of superthermal O(1D) photofragments have been studied by measuring the Doppler profiles of O(1D) as a function of the time delay between photolysis and probe laser pulses. The nascent O(1D) atoms, generated in the photodissociation of O2 by linearly polarized light at 157 nm, have a narrow kinetic energy distribution, centered at 9.8 kcal/mol and a large angular anisotropy. The O(1D) atoms are probed with a tunable vacuum-ultraviolet laser at approximately 115.2 nm. The time evolution of the speed distribution is extracted from the Doppler profiles for each bath gas. The anisotropy parameter distribution as a function of the speed at each time delay is also obtained. The distributions obtained indicate that (a) a collision with He reduces the speed of the O(1D) atom efficiently but only changes slightly the direction of its velocity and (b) a collision with Ne or Ar reduces its speed efficiently and almost randomizes the direction of the O(1D) atom velocity.

ClO radicals are detected by a laser-induced fluorescence technique, using the C 2Σ–X 2Π transition with a tunable vacuum ultraviolet laser system. Predissociation in the C 2Σ state is discussed in terms of the fluorescence lifetime and excitation spectra. The vibrational distribution of ClO produced by the reaction between O1D and HCl is measured.

The interaction of O(1 D 2) with HCl: The initial vibrational distributions in the OH(2Π) produced by chemical reaction, and the HCl(1Σ+) produced by E-V energy transfer J. Chem. Phys. 88, 985 (1988); 10.1063/1.454124Product state distribution in the reaction O(1 D 2)+HCl→OH+Cl Nascent state-resolved ClO͑X 2 ⌸͒ radicals produced in reactions of O͑ 1 D͒ with HCl, CCl 4 , CFCl 3 , CF 2 Cl 2 , and CF 3 Cl have been measured, using vacuum-ultraviolet laser-induced fluorescence of the ClO(C 2 ⌺ Ϫ -X 2 ⌸) transition. Rotational temperatures of ClO ͑X 2 ⌸ 3/2 , vϭ0 and 1͒ are 900-1000 K for chlorofluoromethanes and 2050Ϯ60 K ͑vϭ0͒ and 1770Ϯ180 K ͑vϭ1͒ for HCl. The rotational distribution for the O͑ 1 D͒ϩHCl system is interpreted by the orbital-to-rotational angular momentum transfer mechanism. Vibrational level populations of the ClO͑vϭ0-3͒ products are inverted for CCl 4 and chlorofluoromethanes, but not for HCl. Vibrational excitations in the vϭ0-3 levels are higher for the reactions with the larger available energies.

This paper is dedicated to Professor John C. Polanyi on the occasion of his 65th birthday SAYED MOHAMMED SHAMSUDDIN, YOUSUKE INAGAKI, YUTAKA MATSUMI, and MASAHIRO KAWASAKI. Can. J. Chem. 72, 637 (1994).The photodissociation of ozone at 266, 308, and 532 nm has been studied for O3 + 02(x32;) + [Traduit par la rCdaction]

Doppler profiles of H and D atoms from the reaction S(tD) with HD and a mixture of H and Dz have been measured by a laser-induced fluorescence technique with a vacuum ultraviolet laser. An isotopic channel branching ratio of q, (SD + H)/, (SH + D) is measured to be 0.9 + 0.1 in the reaction of S(ID) + HD at average collision energy Ecol 1.2 kcal/mol. In S(D) + HD, D z, and Hz, the translational energies released are almost the same, 4.6 _+ 0.5 kcal/mol for H and D production channels. The measured branching ratio and translational energy release suggest that the reaction proceeds via a long-lived complex formed by insertion.