Collisional transfer within the Sr(5°J3) multiplet due to nearly adiabatic collisions with noble gases

A time-resolved study of the Sr(5 ${}_{}{}^3{}_{}{}^{}°_J^{}{}_{}{}^{}$) intramultiplet collisional mixing, following optical excitation of the ${}_{}{}^3{}_{}{}^{}\mathrm{°}_1^{}{}_{}{}^{}$ state, is presented. The degeneracy-averaged rate coefficients of Sr(5 ${}_{}{}^3{}_{}{}^{}°_J^{}{}_{}{}^{}$→5 ${}_{}{}^3{}_{}{}^{}°_{J\mathcal{’}}^{}{}_{}{}^{}$) due to collisions with each of the noble gases in a quasiequilibrium cell are derived from least-squares fittings of the triexponential time behavior of 5 ${}_{}{}^3{}_{}{}^{}°_1^{}{}_{}{}^{}$ fluorescence and $5^3$P${\mathrm{°}}_2$, 0→6 ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ absorption data. A 5 ${}_{}{}^3{}_{}{}^{}°_1^{}{}_{}{}^{}$ radiative rate of 22±0.5 μs is also obtained. The dependence of the rates upon buffer pressure demonstrated the presence of both linear and quadratic terms, due to two- and three-body reactions, respectively. The behavior of the binary rate coefficients with varying noble-gas species and temperature is qualitatively consistent with Stückelberg’s model for noncrossing levels.