Moment Analysis of Atomic Spectral Lines

The moments of a spectral line are evaluated in a general way and compared with results which invoke standard assumptions of line-broadening theory. Cesium-rare-gas systems are analyzed for a variety of experimental conditions in the hope of extracting useful information about excited-state interactions. The computation uses atomic-beam results for the ground-state interaction and assumes that the excited-state potentials are represented to a first approximation by Vf=GR¹²-DR⁶. The calculation, which includes a comparison of line shapes, indicates that the following numbers (in cgs units) are reliable for the long-wavelength component of the resonance lines of cesium: with argon, G=4.87×10^-102, D=4.74×10^-58; with helium, G=0.459×10^-102 and D=-0.614×10^-58. Analysis of the cesium-xenon system yields results which illuminate the practical difficulties associated with an otherwise attractive technique.