Prospects for trivalent rare-earth vapor lasers

The exceptionally high volatility of the rare-earth--transition-metal trihalides lend themselves for storing substantial amounts of electronic energy. This is illustrated for NdI3 and Nd-Al-Cl3 vapors for which half of the molecules have been optically pumped. The dynamic nature of these vapor systems are discussed including rotational, vibrational, and electronic degrees of freedom. Implications of the shielded nature of the 4f/sup n/ electrons of the ground electronic configuration (optically active-chemically inactive) are surveyed. Allowed 4f → 5d transitions as pump bands and ligand electronic structure are also discussed. (U.S.)