Temperature and pressure shift of the Cs clock transition in the presence of buffer gases: Ne, N2, Ar

The ground-state hyperfine resonance line of alkali-metal atoms is frequency shifted in the presence of noble or molecular gases. The buffer gases used in vapor-cell atomic clocks thus induce a temperature-dependent shift of the clock transition frequency. We report on measurements of the pressure and temperature dependence of the Cs clock transition frequency in the presence of Ne, Ar, and N-2 buffer gases. The pressure in the sealed glass vapor cells is measured by means of the shift of the Cs D-1 line. We have also investigated the temperature dependence of the optical shift. From these measurements, we infer the pressure and temperature coefficients of the hyperfine frequency shift. It is then possible to predetermine gas mixture ratios that cancel the temperature sensitivity at a given temperature. This prediction is confirmed experimentally for Ar-N-2 mixtures. These results can be useful for improving the long-term frequency stability of Cs vapor-cell clocks.