Shift and Broadening of the ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ 0-0 Line Due to Collisions with Krypton Buffer-Gas Atoms

The shift and broadening of the ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ 0-0 line (frequency 6.8 GHz) due to collisions with Kr atoms have been studied in the pressure range 0.2-10 Torr. The shift versus pressure has been found to be linear and equal to -542 ± 10 Hz/Torr. The linewidth results from the super-position of several effects which are analyzed, one of the most important being the relaxation due to the spin-orbit interaction experienced by Rb atoms while temporarily bound in van der Waals Rb-Kr molecules.