Full- and half-collision studies of metal atom singlet-to-triplet deactivation induced by rare-gas atoms

Experiments and ab initio calculations are described involving singlet-to-triplet deactivation of nsnp(1P) to nsnp(3P) or ns(n - 1)d(3D) valence excited states of Mg, Ca, Sr, Ba, Zn, Cd, and Hg atoms induced by "full" and "half" collisions with rare-gas (RG) atoms. The evidence presented is consistent with a mechanism originally postulated by Breckenridge and Malmin: if an attractive M·RG(1II1) potential curve is crossed by a repulsive M·RG(3Σ1+) potential curve below or near the energy region accessed experimentally, predissociation may occur to form the M(nsnp 3P2) or M(ns(n - 1)d 3D) state. The efficiency of this singlet-to-triplet energy transfer process depends on the magnitude of the spin-orbit coupling which mixes the 1II1 and 3Σ1+ states in the curve-crossing region. © 1995 American Chemical Society.