Two-photon resonant processes in atomic barium vapour

Two-photon resonant or nearly resonant optical processes have been investigated in atomic barium vapour ( approximately 10 17 cm -3 ) with a pulse dye laser (frequency omega L ) covering the range 735-415 nm. These interactions result in strong coherent emissions emitted either forward and backward, or forward only. The optical processes responsible for these coherent emissions have been identified. Seventy five lines (frequency omega ES ) emitted from 1000 to 360 nm are due to optically pumped stimulated emissions or stimulated electronic hyper-Raman scattering. Twenty eight lines (frequency omega sigma ) observed from 795 to 250 nm are generated through four-wave-mixing parametric processes with omega sigma =2 omega L +or- omega ES , and nine- (795-260 nm) through six-wave-mixing parametric processes with omega sigma =2 omega L - omega ES1 - omega ES2 +or- omega ES3 .