SEMICLASSICAL MODEL FOR ELECTRONIC-TO-VIBRATIONAL ENERGY-TRANSFER IN COLLISIONS OF HG(6 P-3(2)) WITH H-2, D2, AND HD

A semiclassical treatment of the 3P1 <-- 3P2 fine-structure transition induced by collisions with diatomic molecules Q = H-2, HD, and D2, is developed, based on the earlier work of Hickman. The model illustrates how the increase of the fine-structure energy splitting provides a new mechanism during collision. This mechanism is due to an additional region of nonadiabatic coupling caused by the anisotropy of the molecule due to its vibration. Actual calculations are reported for collisions of Hg(6(3)P2) with Q in the thermal energy range, using the available HgH2 energy surfaces of this system. The cross sections calculated are in good agreement with the experimental ones in the H-2 and HD cases. The agreement is not so good for D2, which shows that the model has to be improved, probably, by including the molecular rotation.