Differential steric effects in Cl reactions with aligned CHD(v = 1) by the R(0) and Q(1) transitions. II. Abstracting the unexcited D-atoms.

A complete set of four polarization-dependent differential cross sections in the reactions of Cl + aligned-CHD(v=1,jK)→DCl(v=0)+CHD(v=1) is reported here for two different, rotationally polarized states with j = 1: specifically the jK=10 state prepared via the R(0) excitation and the 1±1 state via Q(1). In stark contrast to the complicated situation of the HCl(v) + CD(v = 0) channel reported in Paper-I, the stereo-requirement of this isotopic channel for both polarized reactants appears quite straightforward and consistent with a direct rebound mechanism. The extent of steric effects is moderate and relatively smaller than the alternative H-atom abstraction channel. All major findings reported here can qualitatively be understood by first noting that the present reaction invokes abstracting a D-atom, which is the spectator in the IR-excitation process. Next, it is recognized that the directional properties of two polarized states of CHD(v=1, jK) should manifest primarily in the IR-excited C-H bond, leaving secondary imprints in the unexcited CD-moiety. The stereo-specificity of the DCl + CHD product channel is further reduced by the fact that the abstraction can occur with any one of the three spatially distinct D-atoms.