Hyperfine structure density shift coefficients for K, Rb and Cs at high buffer gas densities

The hyperfine structure (hfs) density and temperature shift has been measured for several alkalies K, Rb, and Cs against the noble gas collision partners He, Ne and Ar at buffer gas densities up to 26000 Torr. The measured shifts have been fitted by an expression dependent on density and temperature yielding as a main new result the quadratic hfs density shift coefficients.