We present a time resolved study of excitation transfer processes between the low lying excited states of barium (6s6p ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_{\mathit{J}}$, 6s5d ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$, 6s5d ${}_{}{}^3{}_{}{}^{}$${\mathit{D}}_{\mathit{J}}$) induced by collisions with noble gases. The transient excited state populations have been measured by means of fluorescence and absorption spectroscopy. Cross sections for spin-changing collisions from ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_1$ to ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$ and from ${}_{}{}^1{}_{}{}^{}$${\mathit{D}}_2$ to ${}_{}{}^3{}_{}{}^{}$${\mathit{D}}_3$ as well as for fine-structure mixing within the ${}_{}{}^3{}_{}{}^{}$D multiplet were obtained by fitting the numerical solution of a seven-state system of rate equations including diffusion to the experimental data. We compare our results to experimental findings for other alkaline earth metals and report an improved value of the lifetime of the 6s6p ${}_{}{}^3{}_{}{}^{}$${\mathit{P}}_1$ state of barium.

• Received 4 May 1995

DOI:https://doi.org/10.1103/PhysRevA.52.2120