Collision induced absorption in mercury–rare-gas collisions

Abstract

The far-wing excitation and probe technique is applied to observe quasimolecular absorption bands on the blue side of the Hg 6 1S0–6 3P2 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(3P2). This gives direct evidence of the assignment of the absorption to the c 31→X 10 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 30+, and B 31 states are also estimated from the analysis for Hg–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.