Collision induced absorption in mercury-rare-gas collisions

The far-wing excitation and probe technique is applied to observe quasimolecular absorption bands on the blue side of the Hg 6 S-1(0)-6 P-3(2) atomic line for the Hg-Ar, Hg-Kr, and Hg-Xe mixtures. It is found that the excitation of this band is followed predominantly by a rapid elastic half-collision scattering on the excited state potential yielding the nascent product state Hg(P-3(2)) This gives direct evidence of the assignment of the absorption to the c (3)1-->X O-1 collision induced dipole transition of the Hg-rare-gas quasimolecules. A chance of nonadiabatic transition from the c state is negligibly small compared to the elastic scattering. Analytical procedures are presented to deduce the c-X transition dipole moment from the relevant potential energy curves by making use of the Hund's coupling schemes of the molecular electronic states. The c-X transition dipole moment is estimated as a function of the internuclear distance and is incorporated into the analysis of the observed band profiles. The potential energy curves of the c, A O-3(+), and B (3)1 states an also estimated from the analysis for HE-Ar and Hg-Kr. The Hg-Xe system shows a small undulation in the c-->X band suggesting that it involves a satellite structure due to an extremum of the c-X difference potential. (C) 1998 American Institute of Physics.