Caesium 6P fine-structure mixing and quenching induced by collisions with ground-state caesium atoms and molecules

Applying the cw laser fluorescence method, the cross sections for the fine structure mixing and quenching of the Cs 6P state, induced by collisions wi th ground-state caesium atoms and molecules, have been measured. Caesium at oms were optically excited to the 5D(J) stares via quadrupole-allowed 6S(1/ 2) --> 5D(J) transitions, while the resonance states were populated by the radiative and collisional 5D(J) --> 6P(J) transitions. The relative populat ions of the Cs 6P(J) sublevels, as well as ratio of the 5D(3/2) to 6P(3/2) populations, were measured as a function of the caesium ground-state number density. From these measurements we obtained the cross section of (14 +/- 5) x 10(-16) cm(2) at T = 585 K for the process CS(6P(1/2)) --> Cs(6P(3/2)) induced by collisions with ground-state caesium atoms. The applied experim ental approach enabled the determination of the effective spontaneous rates for the 6P(J) states which are in agreement with the predictions of Holste in's theory. The cross sections for quenching of 6P(J) by caesium atoms and molecules were measured at T = 635 K and the obtained values are (1.6 +/- 1.4) x 10(-16) cm(2) and (1210 +/- 260) x 10(-16) cm(2), respectively. Usin g recently calculated Cs* + Cs potentials we performed an analysis which sh ows a good agreement between the measured values and the theoretical estima tes.