Abstract

Direct dye laser excitation of the K₂ yellow (566-580-nm), Rb₂ orange (590-610-nm) and Cs₂ near-infrared (702-722-nm) diffuse bands has been investigated. Experimental results are consistent with $2^3{\Pi }_g\text{(bound)}\leftarrow 1^3{\Sigma }_u^{+}\text{(free)}$ excitation followed by bound → free fluorescence. For Rb₂ and Cs₂, spin-orbit interactions become so significant that the 2³Π_g state is strongly split into three independent component states and this is observed in the spectra. We have investigated the free-bound-free fluorescence of the K₂ yellow diffuse band in particular detail. Theoretical treatment and quantum-mechanical simulation of free-bound-free resonance fluorescence are described for comparison with our single longitudinal mode dye laser direct excitation experiments and measurements of the weak absorption in the same spectral region.

© 1986 Optical Society of America