Laser-induced fluorescence studies of elementary processes in a helium plasma following He 3(3)P-2(3)S and 3(1)P-2(1)S excitation

We report experiments in which laser-induced fluorescence detection is inco rporated into a flowing afterglow helium plasma to study the kinetics and d ynamics of excited helium atoms. Following excitation of helium in the 3 P- 3, 3 S-3 band at 388.9 nm, dispersed fluorescence spectra show major featur es at 388.9, 706.5 and 587.6 nm corresponding to emission from the 3 P-3, 3 S-3 and 3 D-3 states as observed in previous studies. In addition to these major features, we also observe weaker, molecular emissions in the 430-500 and 710-725 nm regions which we assign to fluorescence from He;? states. S imilar experiments in which the 3 P-1-2 S-1 band at 501.6 nm is excited aff ord strong atomic fluorescence from the 3 P-1 and 3 D-1 states at 501.6 and 667.8 nm, respectively. A weak emission feature can also be assigned to 3 S-1-2 P-1 emission at 728.1 nm. Weak molecular emissions are again observed but in this case in the 440-470 and 535-600 nm regions.