Fluorescence dip spectroscopy of sodium atoms in an inductively coupled plasma

Abstract

Two dye lasers were used to pump sodium atoms present in an inductively coupled plasma to the 4 d levels via 3 s-3 p excitation. By monitoring the fluorescence of both yellow lines while scanning the second laser, two dips were observed when the second laser was tuned to 568.263 nm ( 2 P 1 2 - 2 D 3 2 )and to 568.820 nm ( 2 P 1 2 - 2 D 5 2 , 3 2 ). The plots of the reciprocal relative fluorescence dips as a function of the reciprocal spectral energy density of the second laser (second excitation step) resulted in straight lines with slopes proportional to the quantum efficiencies of these transitions and therefore to the spontaneous transition probabilities. The experimental ratio between the gA values obtained by this method is compared to that calculated from tabulated values. In addition, the absolute values of excited state quantum efficiencies derived from these plots as well as from the saturation curves of the fluorescence dips are discussed in terms of possible ionization losses from the 4 d levels.