The relaxation of hyperfine orientation indirectly induced by optical pumping with σ-polarized D<sub>1</sub>-light in a cesium vapor in the presence of Ar is experimentally studied. The detection technique ensures the absence of quadrupole relaxation contributions in the relaxation signals. The results from the dependences of the hyperfine relaxation rate on the temperature and argon pressure are: diffusion coefficient of Cs in Ar, <i>D</i><sub>0</sub> = 0.101 ± 0.010 cm<sup>2</sup>s<sup>−1</sup> at 0°C and 760 Torr; relaxation cross section by Cs-Ar collisions, σ<sub>c</sub> = (104 ± 5) × 10<sup>−23</sup>cm<sup>2</sup>; relaxation cross section by Cs-Cs (spin exchange) collisions, σ<sub>ex</sub> = (1.63 ± 0.13) × 10<sup>−14</sup> cm<sup>2</sup>.
J. Tornos and J. C. Amare, "Hyperfine Relaxation of an Optically Pumped Cesium Vapor," Appl. Spectrosc. 40, 596-599 (1986)