DOPPLER-FREE SATURATION FLUORESCENCE SPECTROSCOPY OF NA ATOMS FOR ATMOSPHERIC APPLICATION

The well-known theory of absorption and fluorescence is briefly review ed in a systematic manner for the Na D transitions. The resulting form alism is applied to simulation of Doppler-free saturation fluorescence spectra. With only one adjusting parameter, the nonradiative rate cho sen to represent the time a thermal atom takes to move across the lase r beams, the simulated Doppler-free spectra match the measured ones we ll for both D-1 and D-2 transitions over one-decade of excitation inte nsities. Relative to the weighted center of the six D-2 hyperfine tran sition lines, the frequencies of the dominant Doppler-free features ha ve been determined from a simulated spectrum to within +/-0.1 MHz to b e -651.4, 187.8, and 1068.0 MHz, respectively, for D-2a, crossover, an d D-2b resonances. These features may be used as accurate frequency re ferences for atmospheric spectroscopy. They are essential for the oper ation of the newly developed narrow-band Na fluorescence lidar for win d and temperature measurements in the mesopause region.