Experimental studies of two-photon absorption of sodium perturbed by collisions with noble gas atoms

This study was performed with sodium vapor at about 300°C perturbed by noble gases at densities between 0.5 x 10¹⁹ and 6 x 10¹⁹ atoms/cm³. We have measured the rate of two-photon absorption for step-wise processes, which occur if the exciting frequency is resonant with one of the transition frequencies ω_ri or ω_fr with i, r, and f referring, respectively, to the initial, the relay and the final state. By varying the exciting frequency, we obtain collision profiles which may be difficult to obtain by other methods. The shifts and widths for the transitions 3S-3P_{$\text{3}\text{2}$}, 3S-3P_{$\text{1}\text{2}$}, and 3P_{$\text{3}\text{2}$}-5S have been measured for several noble gases. The observed variation of the profiles with perturber gas pressure suggests possible quenching of the relay state by noble gas molecules present in the mixture.