Fine-structure mixing in72Dand82DRb atoms, induced in collisions with ground-state atoms and molecules

Cross sections for $7^{2}D$ and $8^{2}D$ fine-structure mixing in Rb, induced by collisions with various ground-state atoms and ${\mathrm{N}}_2$ molecules, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a buffer gas, was irradiated in a glass fluorescence cell with pulses of radiation from a ${\mathrm{N}}_2$ laser-pumped dye laser, populating a ${}_{}{}^2{}_{}{}^{}D$ fine-structure state by two-photon absorption. The resulting fluorescence included a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. Measurements of relative intensities of the two components in relation to buffer-gas pressure yielded the following cross sections (in units of ${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$): $Q(7^2{D}_{\frac{3}{2}}\to 7^2{D}_{\frac{5}{2}})=14.1,15.5,\mathrm{and}10.0$; $Q(7^2{D}_{\frac{3}{2}}\leftarrow 7^2{D}_{\frac{5}{2}})=9.0,10.5,\mathrm{and}6.9$, for Kr, Xe, and ${\mathrm{N}}_2$, respectively; $Q(8^2{D}_{\frac{3}{2}}\to 8^2{D}_{\frac{5}{2}})=8.9,4.9,12.4,24.9,25.8,12.1,\mathrm{and}43.1$; $Q(8^2{D}_{\frac{3}{2}}\leftarrow 8^2{D}_{\frac{5}{2}})=5.8,3.2,9.4,15.1,17.6,8.3,\mathrm{and}28.5$, for He, Ne, Ar, Kr, Xe, ${\mathrm{N}}_2$, and Rb, respectively. Cross sections for the effective depopulation of the ${}_{}{}^2{}_{}{}^{}D$ states were also determined.