LiAr, LiKr and LiXe excimers: Photochemical formation of the 3(2)Sigma(+)-1(2)Sigma(+) bands

We investigated the photochemical formation of lithium-rare-gas excimers in the 3(2)Sigma(+) state through the reaction of Li-3(2(C)(1)Pi(u)) and the ground-state rare-gas atom. Lithium-rare-gas vapor mixture was prepared in the heat-pipe oven. We populated the 2(C)(1)Pi(u), state of the Lit molecul e using the XeCl excimer laser wavelength at 308 nm or the PTP dye laser wa velength at about 335 nm. The 3(2)Sigma(+)-1(2)Sigma(+) transitions were ob served with peaks at 414, 420 and 435 nm for LiAr, LiKr and LiXe, respectiv ely. We estimated thermally averaged rate constants for these photochemical reactions, which are (2.3 +/- 1.1) 10(-10) cm(3)s(-1) for LiAr, (6.9 +/- 3 .2) 10(-10)cm(3)s(-1) for LiKr and (19 +/- 9) 10(-10)cm(3)s(-1) for LiXe. A b initio potential-energy curves and transition dipole moments for LiKr wer e calculated applying the SCF MRT)CI method. Available data for the LiAr an d LiKr(r excimers are presented, including potential-energy curves, electro nic transition dipole moments, and spectroscopic constants. Possible photoc hemical formation of these molecules in the excited states is discussed. We performed the quantum-mechanical spectral simulations of the LiAr and LiKr 3(2)Sigma(+)-1(2)Sigma(+) transitions, using ab initio potential-energy cu rves.