Experimental fine-structure branching ratios for Na–rare-gas optical collisions

Experimental ratios for branching into the fine-structure levels of the Na 3p multiplet, as a consequence of an optical collision with He, Ne, Ar, Kr, or Xe, are reported. The process studied is Na(3s ${}_{}{}^2{}_{}{}^{}S_{1/2}^{}{}_{}{}^{}$)+scrR+nhν→ Na(3p ${}_{}{}^2{}_{}{}^{}P_j^{}{}_{}{}^{}$)+scrR+(n-1)hν , where scrR represents a rare-gas atom and where the laser frequency ν is tuned in the wings of the Na resonance transitions. The branching ratios are defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Na D1 and D2 lines. The ratios are determined for detunings ranging from about 650 ${\mathrm{cm}}^{\mathrm{-}1}$ in the blue wing to 170 ${\mathrm{cm}}^{\mathrm{-}1}$ in the red wing of the Na 3p multiplet. The branching is found to be strongly detuning dependent in the vicinity of the NaAr, NaKr, and NaXe near-red-wing satellites. The blue-wing branching ratios show a detuning-dependent approach to a recoil, or sudden statistical, limit of 0.5, irrespective of the rare gas. Fine-structure changing cross sections have also been measured for resonant excitation of the Na 3p ${}_{}{}^2{}_{}{}^{}P_j^{}{}_{}{}^{}$ state; the results are consistent with cross sections obtained from wing excitation.