Resonant Reaction in Rb--Cs Vapour Mixture Rb(5P_1/2) + Cs(6P_3/2) → Cs(8S_1/2)+Rb(5S_1/2)

We experimentally study energy-pooling collision in the Rb--Cs vapour mixture at low densities in a cell. Atoms are excited to Rb(5P_1/2) and Cs(6P_3/2) states using two single-mode diode lasers. To isolate the heteronuclear contribution in the fluorescence spectrum, a double-modulation technique is adopted. The excited-atom density and spatial distribution are mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam, tuned to Rb(5P_1/2 → 7S_1/2) and Cs(6P_3/2 → 8S_1/2) transitions, respectively, which could be translated parallel to the pump beams. The excited atom densities are combined with the measured fluorescence ratios to determine cross section for the energy-pooling process i.e. Rb(5P_1/2) +Cs (6P_3/2) → Cs(8S_3/2)+Rb (5S_1/2). The cross section is 3.79×10^-14cm² ± 45%.