Comparative study of the photoassociation reaction of He + X+→ HeX+ (X = H, D): Including multiphoton transitions and dissociations

Abstract

AbstractUsing the time‐dependent quantum wave packet method, the photoassociation (PA) processes of He + H +→ HeH+ and He + D +→ HeD+, driven by the sin2‐shaped femtosecond laser pulse in the electronic ground state, including multiphoton transitions and dissociations, are investigated for a wide range of initial collision momenta spanning from 1 to 4 a.u. (or for the collision energy roughly in the ranges of 0.009∼0.148 eV and 0.006∼0.089 eV for HeH+ and HeD+ systems, respectively). It is found that, at some collision momenta, multiphoton transitions to deeply bound states are inevitable to occur and can greatly decrease the PA probability of the target state that selected is the vibrational state v = 6. For the dissociation process, the higher‐order (two‐ and three‐photon) dissociations, measured from the target state, tend to be significant at relative high collision energies, which implies that above‐threshold dissociations may also be an important loss mechanism in the PA process. In addition, it is also shown that the higher‐order dissociation is much stronger for HeH+ systems than that for HeD+ systems at a given collision momentum, and could be enhanced by the strong transitions among deeply bound states.