Theory of transient anisotropy in molecular photodissociation

摘要

In this paper, we examine how vector properties of photodissociation with a coherent laser pulse evolve in time during and after the excitation process. In particular, we define and explore thetransientanisotropy parameter bgr;(t). We apply our formulation to the case of the predissociation of the NaI molecule. We predict that under certain conditions, bgr;(t) displays abeatingphenomenon, in which the system oscillates periodically between a parallelhyphen;type and a perpendicularhyphen;type angular distribution. Depending on the excitation pulse, this lsquo;lsquo;vectorialrsquo;rsquo; beating may be accompanied by a faster beating similar to the lsquo;lsquo;scalarrsquo;rsquo; vibrational beating observed in the past in the NaI system. It is shown that the transient anisotropy beating may be used to obtain experimentally the timehyphen;dependent average interfragment separation, and that differentJstates are characterized by different interfragment separation curves. thinsp;