Diatomic excimer dynamics in microplasma lamps and alkali lasers

Abstract

The dynamics of diatomic excimers - electronically excited molecules having dissociative ground states - generated in alkali-rare gas mixtures and low temperature microplasmas have been pursued and the experimental and computational results are presented here. This work focuses on the Cs-rare gas and He2 molecules that are of considerable interest as efficient near-infrared lasers, or as the energy source for driving the Hg+ vacuum-ultraviolet lamp (194.2 nm). The photoassociation and subsequent stimulated emission of cesium (Cs) - rare gas (Ar or Xe) pairs were examined by laser pump-probe experiments, and an optical-to-optical energy conversion efficiency of ~28% was observed when Cs-Ar pairs were pumped at 836.7 nm and stimulated emission occurs at 852.2 nm. By comparing full quantum simulations of Cs-Xe photoassociation to the gain spectrum of Cs-Xe in the red satellite of the Cs D2 line, it is shown that the structure of weakly bound Cs-Xe molecules (including the dissociation energy), correlated with Cs(62P3/2) + Xe(5p6 1S0) in the separated atom limit, can be determined with precision. Extensive studies of time-resolved emission from the Hg+ ion in electrically driven microplasma lamps show that the Hg+ line at 194.2 nm is pumped efficiently by Penning ionization of the Hg atom by metastable helium molecules. Experimental results as well as zero-dimensional kinetic simulations support the validity of the proposed kinetic pathway.