Energy-Pooling Collisions in Rubidium： 5P3/2 ＋ 5P3/2 → 5S ＋ （nl = 5D, 7S）

We experimentally study rubidium energy pooling collisions of Rb（SP3/2） ＋ Rb（5P3/2） → Rb（5S1/2） ＋ Rb （nlJ = 5DJ, 7S1/2） at low densities in a cell using diode laser excitation. The excited-atom density and spatial distribution are mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam, tuned to the 5P3/2 → 7S1/2 transition, which could be translated parallel to the pump beam. The excited atom densities are combined with measured fluorescence ratios to determine cross sections for the rubidium energy pooling process. The cross sections for nlJ being 5D5/2, 5D3/2, and 7S1/2 are （1.32±0.59）×10^-14, （1.18±0.53）×10^-14 and （3.21±1.44）×10^-15cm^2, respectively.