Collisional energy transfer between excited-state strontium and noble-gas atoms.

Abstract

Inert-gas-induced collisional transfer between the first four excited states of Sr has been measured by determining excited-state densities following pulsed laser excitation of the 5 $^{1}$P state. We observe 5 $^{1}$P collisional transfer exclusively to the 4 $^{3}$D state, with (\ensuremath{\sim}800 K) rate coefficients ranging from 0.24 to 2.0\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ for the various gases. We also measure 4 $^{1}$${\mathit{D}}_{2}$ transfer primarily to the 4 $^{3}$D state, with rate coefficients of 0.65 to 6.8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The 4 $^{3}$D state radiative lifetime is observed to be 2.9\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}s, collisional mixing between the 4 $^{3}$${\mathit{D}}_{\mathit{j}}$ fine-structure levels is essentially gas kinetic (k\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$), and k${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ for 4 $^{3}$D\ensuremath{\rightarrow}5 $^{3}$P collisional transfer.