Collisional electronic and rotational relaxation of molecular helium in an afterglow of pulsed discharge

The selective excitation with a dye laser was carried out from He2(2sa3Σsub(u)sup(+), v''=0, J'') metastable state to He2(3pπe3PI sub(g), v'=0, J') state in the afterglow of a pulsed He discharge. The filling gas pressure was 10 Torr. The rotational levels from J'=1 to 9 of He2(3pπe3PI sub(g), v'=0) were pumped through the eleven transitions and the fluorescence light due to the excitation transfer was observed from many rotational levels in v'=0 of He2(3pπe3PI sub(g)), He2(3sd3Σsub(u)sup(+)), He2(3dσf3Σsub(u)sup(+)), He2(3dπf3PI sub(u)) and He2(3d delta f3Δsub(u)) in the spectral ranges of 4600-4700 A, 6380-6480 A, 5930-6000 A, 5850-5930 A and 5710-5740 A, respectively, with a boxcar averager connected to a monochromator. The temporal change of the fluorescence lines gives the lifetime of about 1 x 10-8 s for the all electronic states except for He2(3sd3Σsub(u)sup(+)). The fluorescence line from He2(3sd3Σsub(u)sup(+)) state shows a long lifetime which increases with decreasing J' value. (auth.)