Absorption Coefficients for the Wings of the First Two Resonance Doublets of Cesium Broadened by Argon

Measurements are reported of the absolute absorption coefficients in the wings of the 8944-, 8521-, 4593-, and 4555-Å resonance lines of cesium in the presence of argon at densities between about 6 × ${10}^{18}$ and 2 × ${10}^{19}$ atom ${\mathrm{cm}}^{-3\mathrm{}}$. The data extend from about 0.7 Å to as much as 600 Å from the line center and were obtained using cesium densities between 7 × ${10}^{11}$ and 2 × ${10}^{15}$ atom ${\mathrm{cm}}^{-3\mathrm{}}$ and temperatures between 390 and 470°K. The measured absorption coefficients are proportional to the product of the cesium and argon densities as expected from line broadening produced by binary collisions between cesium and argon atoms. Using the quasistatic theory as a guide for interpretation, the line profiles for wings of the first resonance doublet show a transition from a wavelength dependence determined by long-range van der Waals forces to a dependence determined by the short-range internuclear potentials discussed by Hedges, Drummond, and Gallagher (HDG). The far-wing absorption profiles obtained in the present experiments are in good agreement with those calculated from the fluorescence data of HDG.