The collision cross sections for the fine-structure mixing of caesium 6P levels induced by collisions with potassium atoms

The cross section for the fine-structure excitation transfer Cs(6P1/2) → Cs(6P3/2), induced by collisions with the ground state potassium atoms, has been measured by resonant Doppler-free two-photon spectroscopy. The population densities of caesium 6PJ (J = 1/2, 3/2) levels were probed by thermionic detection of the collisionally ionized caesium atoms from the Cs(6PJ) → Cs(10S1/2) excitation channel. The cross section for the transfer process at the temperature T = 503 K has been found to be σ(1/2 → 3/2) = 45 A2 ± 20%. The result is compared with previously published experimental cross sections for fine-structure transfer in resonance states of other alkali elements perturbed by potassium and a theoretical value of the Li(2PJ)-K system calculated in a simple approach. (orig.)