Fluorescence monitoring of laser induced population changes of 6P and 6D levels in cesium vapor

Observations of enhancement and reduction of the fluorescence intensity in the continuous-wave excitation of Cs atomic vapor is reported. The reduction is due to a depopulation of the 62Po3/2 state upon illumination of a Cs vapor cell with light corresponding to the 62Po3/2→62D5/2 transition (917.23 nm). Collisional relaxation of the 62D5/2 atoms to the 62D3/2 state, followed by radiative decay to the 62Po1/2 state (876.14 nm), creates an increase in the population of the 62Po1/2 state. The increase in the excited state population results in an increase in the fluorescence intensity of the 62Po1/2→62S1/2 transition (894.35 nm). These laser induced population changes, monitored by the decrease or increase of the corresponding fluorescence signals, were modeled using a simplified density matrix formalism, which allowed an order of magnitude estimate of the rates of level mixing between 62D states and 62P states.