Energy pooling in caesium vapour: $\mathsf{ Cs^*(6P_{J})+Cs^*(6P_{ J'})\rightarrow Cs(6S)+Cs^{**}(6D)}$

The total rate coefficient κ for the energy pooling process Cs * (6P) + Cs * (6P) → Cs(6S) + Cs ** (6D) has been measured in dependence on the ratio of the number densities of the Cs 6P fine-structure sublevels. The measurements were performed applying the laser fluorescence method. From the set of the obtained data for k, the rate coefficients for the particular Cs * (6P J ) + Cs * (6P J' ) collisions were derived. The obtained values for the Cs * (P 1/2 ) + Cs * (P 1/2 ), Cs * (P 1/2 ) + Cs * (P 1/2 ) and Cs * (P 3/2 ) + Cs * (P 1/2 ) collisions at T = 600 K are κ 1 = 2 x 10 -9 cm 3 s -1 , κ 2 = 3.1 x 10 -10 cm 3 s -1 and κ 3 < 3 x 10 -10 cm 3 s -1 , respectively. The value for κ 1 and the estimate for κ 3 are consistent with the data previously published by other authors. The rate coefficient κ 2 is reported for the first time.