Vibrationally state-resolved differential cross sections ͑DCS͒ and product rotational distributions have been measured for the ClϩHD(vϭ1, Jϭ1)→HCl͑DCl͒ϩD͑H͒ reaction at a mean collision energy of 0.065 eV using a photoinitiated reaction ͑''photoloc''͒ technique. The effect of HD reagent rotational alignment in the ClϩHD(vϭ1, Jϭ2) reaction has also been investigated. The experimental results have been compared with exact quantum mechanical and quasiclassical trajectory calculations performed on the G3 potential energy surface of Allison et al. ͓J. Phys. Chem. 100, 13575 ͑1996͔͒. The experimental measurements reveal that the products are predominantly backward and sideways scattered for HCl(vЈϭ0) and HCl(vЈϭ1), with no forward scattering at the collision energies studied, in quantitative agreement with theoretical predictions. The experimental product rotational distribution for HCl(vЈϭ1) also shows excellent agreement with quantum-mechanical calculations, but the measured DClϩH to HClϩD branching ratio is near unity, which is at variance with the theoretical calculations that predict about 3 times larger yield of HClϩD at these collision energies. The reactivity shows a marked dependence on the direction of the HD(vϭ1, Jϭ2) rotational angular momentum, and experimental measurements of this reagent alignment effect are in good agreement with theoretical predictions.

Femtosecond ͑fs͒ dynamics of reactions of cyclic ethers, symmetric and asymmetric structures, are reported. The diradical intermediates and their ␤-cleavages, which involve simultaneous C-C, C-H -bond breakage and C-O, C-C -bond formation, are observed and studied by fs-resolved mass spectrometry. To compare with experiments, we present density functional theory calculations of the potential energy surface and microcanonical rates and product distributions.