Terbium chloride--aluminum chloride vapor system. II. Fluorescence

Measurements of the fluorescence spectra and fluorescence decay kinetics of the vapor complex formed at elevated temperatures between TbCl3 and AlCl3 have been made in the 350 to 700 nm wavelength range. The principal lines in the spectra were identified as emission from the 5D4, 5D3, and the 5G6 energy levels of the Tb3+ ion. The radiative lifetime of the 5D4 level at low temperatures was found to be 3.88 ms, and was used to determine the oscillator strenghts of the 5D4→7F/sub J/ (J=0 through 6) transitions after their branching ratios were measured. The peak cross section for stimulated emission on the strong 5D4→7F5 transition was found to be 2.87 x 10-21 cm2 at lambda=543 nm. A population inversion of 1018 cm-3 could produce a small signal gain of 30% per meter on this transition, indicating that laser emission may be possible at temperatures where sufficient vapor density can be obtained