Interpretation of Foreign-Gas Broadening and Shift in Krypton

Collision broadening and shift due to low pressures of He, Ne, Ar, and Kr have been measured for two emission lines of krypton at temperatures of 80 and 295°K. Different perturbing gases are found to produce widely different temperature dependencies of line shift and line broadening. These results are interpreted in terms of the Lindholm-Foley "impact theory" of collision broadening, assuming a Lennard-Jones (12-6) interaction between radiating and perturbing atoms. Semiquantitative agreement of theory and experiment is found in the case of helium perturbers; the results for neon perturbers are described with striking accuracy. Agreement in the case of argon perturbers is less good. As expected, for the line with a metastable lower level, the krypton-krypton broadening data are consistent with the extreme of a Van der Waals $r^{-6\mathrm{}}$ interaction.