Measurement Of Fine Structure Branching Ratios For Rb-He Optical Collisions

Excited state rubidium atom densities and fine-structure branching ratios for Rb-He optical collisions have been measured in the present paper. The detailed information of the two progress is given as follows:(1) Experimental ratios for branching into the fine-structure levels of the Rb5P multiplet, as a consequence of an optical collision with He are reported. The process studied is Rb(5S1 /2 )+He+hν→Rb(5PJ )+He, where the pulsed laser frequency is tuned in the wings of the Rb resonance transitions. As RbHe molecular state correlate to the two 52PJ states, there is some likelihood that the molecule will dissociate into 52P1/2 or 52P3/2 state. The ratios are determined for detuning from about 200 cm-1 in the blue wing to 180 cm-1 in the red wing of the Rb5P multiplet. The branching ratios and cross sections for collision 5P1/2→5P3/2 transition are obtained. The blue-wing branching ratios show a detuning-dependent approach to limit of 0.2. The branching is found to be very large (~ 40) in the red wing, irrespective of the detuning. Fine structure changing cross section [( )1.1±0.3×10 ?17 cm2] has been measured from wing excitation; the result is consistent with cross section obtained for resonant excitation of the Rb5PJ state.(2) Excited state population distribution created by 5S1/2→5P3/2 laser excitation in room temperature rubidium vapor mixed with H2 was quantitatively analyzed applying absorption and saturation spectroscopy. When the laser line width is much smaller than the Doppler line width, the absorption coefficients were measured for a series of P780 powers between 40μW and 5mW. Population in the 5P3/2 level obtained from the saturation measurements was also determined by the absorption measurement of narrow spectral line from a Rb hollow cathode lamp. The agreement between the results obtained in these two ways is very good.