Preferential scattering of one isotopomer over another in (He, HD+) collisions

Differential cross-section for both the channels of the reaction He + HD+ (v = 0, 1,  2, 3; j = 0) → HeH(D)+ + D(H) has been calculated using the time-dependent quantum mechanical methodology (helicity basis truncated at k = 2) on the Palmieri et al. potential energy surface at relative translational energy Etrans= 1.0 eV. It is shown that HeH+ would be formed preferentially over HeD+ in the forward direction, while HeD+ would be preferred over HeH+ in the backward direction for v = 1, 2, 3. For v = 0, HeH+ is scattered preferentially over HeD+ in all directions. Therefore, the isotopic branching ratio and its dependence on product scattering angle can be a sensitive probe of the potential energy surface.