CALCULATIONS OF INELASTIC-COLLISIONS OF EXCITED-STATES OF XE WITH HE AND AR

Coupled channel calculations of thermal collisions of Xe(5p5nl) (nl = 6s,6p,5d) with He and Ar have been performed using potential curves and coupling matrix elements that we previously calculated. Coupling among all of the closely spaced 6s', 6p, and 5d fine structure levels of Xe is fully included. These excited levels lie in the range 76 000-84 000 cm-1 above the Xe ground state, and the spacing of adjacent levels ranges from 84 to 1460 cm-1. Rate constants for level-to-level transitions are calculated at T = 300 and T = 800 and compared with recent experiments; agreement is generally good. The rate constants are very sensitive to the specific initial and final levels and to the collision partner. This sensitivity can be explained by the pattern of crossings and avoided crossings of potential curves corresponding to individual fine structure levels. The calculations thereby illustrate the importance of spin-orbit effects in heavy atom systems and provide insight into a large amount of data.