Production of excited cesium ions in helium-cesium afterglows

Studies of the time dependencies of the Csii spectral emission and ${\mathrm{He}}^m\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$ number density were made during the decay period of plasmas produced in helium-cesium gas mixtures. Transitions originating from 15 Csii energy levels (in the spectral range from 380 to 750 nm) were observed in the afterglow. One Csii energy level is produced by the Penning ionization of Cs by ${\mathrm{He}}^m\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$. Six Csii excited states are populated by charge exchange between ${\mathrm{He}}_2^{+}$ and Cs, and the remaining Csii energy levels are formed by an excitationtransfer process between ${\mathrm{He}}^m\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$ and ${\mathrm{Cs}}^{+}$. No evidence was found for the production of excited cesium ions by charge transfer between ${\mathrm{He}}^{+}$ and Cs. A value of 7×${10}^{-10\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$ was measured for the reaction-rate constant for energy exchange between ${\mathrm{He}}^m\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$ and Cs.