Depolarization of6P322cesium atoms, induced in collisions with noble gases

Cross sections for relaxation of circular and linear polarization of $6{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-Å Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\overrightarrow{\mathrm{I}}$ is coupled to the electronic angular momentum $\overrightarrow{\mathrm{J}}$, the measurements yielded depolarization cross sections $Q(\mathrm{circ}.\mathrm{})$ and $Q(\mathrm{lin}.\mathrm{})$, which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\overrightarrow{\mathrm{I}}$ and $\overrightarrow{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.