Collisional excitation transfer in near-resonant processes: application to H+D

Abstract

The excitation-transfer process between S- and P-state atoms is investigated theoretically by the impact-parameter method. With respect to the P states of an atom, all three degenerate states of mutually orthogonal polarization are taken into account. This yields coupled differential equations which can be solved numerically by the Runge-Kutta-Gill method. As a typical example, the cross section for the excitation transfer between H and D is calculated numerically. The cross section is found to have its maximum 420 pi a02 at a relative velocity of about 1.5 v0, where a0 is the Bohr radius and v0 is the thermal velocity at 300K. In the high-energy region, the decrease of the cross section is inversely proportional to the relative velocity.