Ion formation in laser-irradiated cesium vapor

We study theoretically the formation of Cs+ and Cs2+ during cw laser radiation resonant with 6s-7p transition of Cs atomic vapor. This is done by numerically solving rate equations for the evolution of atomic state and electron populations. The results of calculations for the atomic and molecular ions density at different values of laser power clarified that the associative ionization and Penning ionization process play an important role for producing the Cs2+ and Cs+, respectively, during the plasma formation. Also, the results showed that laser power of the order of 150 mW and 40-50 ns irradiation time are optimal in producing a fully ionized plasma.