Experimental ratios for branching into the fine-structure levels of the Rb 5P multiplet

as a consequence of an optical collision with ground state Rb atoms are reported.The laser frequency ν is tuned in the red wing of the Rb resonance transition.The branching ratios are defined as I(D1)/I(D2)

where I(D1)and I(D1)are measured intensities of the atomic Rb D1 and D2 lines.The ratios are determined for detunings ranging from about 15 to 50cm~-1 in the red wing of the Rb state.The branching is found to be strongly detuning dependent in the vicinity of the Rb 5P3/2 near-red-wing.Fine-structure changing cross section has also been measured for Rb 5~22PJ state.The cross section σ_21 is 3.2×10~-15cm2.