Measured Absolute Cross Sections for K* + Rb Collisional Excitation Transfer

The electronic excitation transfer processes, $\mathrm{K}\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)\to \mathrm{Rb}\left({}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)\to \mathrm{K}\left({}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)+\mathrm{Rb}\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)+\Delta E$ and $\mathrm{K}\left({}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\right)+\mathrm{Rb}\left({}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)\to \mathrm{K}\left({}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\right)+\mathrm{Rb}\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)+\Delta E$ have been studied by irradiating a cell containing a nonequilibrium mixture of potassium and rubidium vapors with either the 7665 Å D2 line or the 7699 Å D1 line of the potassium resonance doublet. The resulting collisionally induced rubidium 7948 Å fluorescence signal, isolated by interference filters used in tandem, is detected with a liquid-nitrogen-cooled $S-1\mathrm{}$ photo-multiplier placed at right angles to the direction of excitation. Measurements of the intensity ratio of the potassium and rubidium fluoresence combined with an optical absorption determination of the rubidium atom density yields the following excitation transfer cross sections: $Q\left[\mathrm{K}\right({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{})\to \mathrm{Rb}({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\left)\right]=2.2\mathrm{} {\AA }^2\pm 25\%$ and $Q\left[\mathrm{K}\right({}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{})\to \mathrm{Rb}({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\left)\right]=2.6\mathrm{} {\AA }^2\pm 20\%$ at $T=365\mathrm{}°\mathrm{K}\pm 2\%$. Throughout an experimental run the potassium and rubidium vapor pressures are varied, but data are taken for only the lowest vapor pressures for which corrections due to resonance radiation imprisonment are unnecessary.