LiAr, LiKr and LiXe excimers: Photochemical formation of the $\mathsf3^{2}\Sigma^{+} $ - $\mathsf1^{2}\Sigma ^{+}$ bands

Abstract

We investigated the photochemical formation of lithium-rare-gas excimers in the 3\(\) state through the reaction of Li2(2(C)\(\)) and the ground-state rare-gas atom. Lithium-rare-gas vapor mixture was prepared in the heat-pipe oven. We populated the 2(C)\(\)state of the Li2 molecule using the XeCl excimer laser wavelength at 308 nm or the PTP dye laser wavelength at about 335 nm. The 3\(\)-1\(\) transitions were observed with peaks at 414, 420 and 435 nm for LiAr, LiKr and LiXe, respectively. We estimated thermally averaged rate constants for these photochemical reactions, which are \(\)cm3s-1 for LiAr, \(\)cm3s-1 for LiKr and \(\)cm3s-1 for LiXe. Ab initio potential-energy curves and transition dipole moments for LiKr were calculated applying the SCF MRDCI method. Available data for the LiAr and LiKr excimers are presented, including potential-energy curves, electronic transition dipole moments, and spectroscopic constants. Possible photochemical formation of these molecules in the excited states is discussed. We performed the quantum-mechanical spectral simulations of the LiAr and LiKr 3\(\)-1\(\) transitions, using ab initio potential-energy curves.