Hyperfine pressure shift ofCs133atoms in noble and molecular buffer gases

The fractional pressure shifts (fps) of the ground-state hyperfine frequency of ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$ were remeasured for a number of buffer gases and found to be (in units of ${10}^{-9\mathrm{}}$/Torr): for He, 123.5 ± 1.0; ${\mathrm{H}}_2$, 118.0 ± 0.5; Ne, 63.5 ± 0.5; ${\mathrm{N}}_2$, 90.0 ± 1.0; Ar, -21.5 ± 1.0; ${\mathrm{CH}}_4$, -104.0 ± 0.5; ${\mathrm{CD}}_3$H, -92.5 ± 0.5; ${\mathrm{C}}_2$ ${\mathrm{H}}_6$, -118.5 ± 2.5; ${\mathrm{C}}_3$ ${\mathrm{H}}_8$, -291.5 ± 1.5; ${\mathrm{C}}_4$ ${\mathrm{H}}_{10}$, -390.5 ± 2.5; and ${\mathrm{C}}_2$ ${\mathrm{H}}_4$, -269.0 ± 2.5. In addition, the fps for the buffers ${\mathrm{D}}_2$, 188.0 ± 0.5; ${\mathrm{CF}}_4$, -21.5 ± 1.0; and ${\mathrm{CD}}_2$ ${\mathrm{H}}_2$, -95.5 ± 0.5 were measured for the first time. Trends in the observed fractional shifts are discussed qualitatively in terms of the effects of anisotropic intermolecular interactions on the long-and short-range contributions to the fps.