Measurements of collisional depolarization cross sections play an important role in gaining valuable information about the interaction between inert and rare-gas atoms.A key element in understanding collisional dynamics is the detailed analysis of the polarization of the emitted photons.In order to investigate the collisional cross section of the excited J=1/2 cesium atoms, by collisions with the ground level argon atoms, experimental measurements were made studying circular polarization spectra.Orientation in the J=1/2 level was optically induced by circularly polarized light with a positive helicity.A two-photon double-resonance (6s 2 S 1/2 →6p 2 P 1/2 → 10s 2 S 1/2 ) condition was achieved using nanosecond pulsed dye lasers, and the intensity of the cascade fluorescence was monitored in the presence of argon atoms ranging from 10 -4 torr to 100 torr.
We have experimentally investigated the anisotropy-dependent circular polarization spectra of the
133Cs $6s^{2}S_{1∕2}\ensuremath{\rightarrow}6p^{2}P_{3∕2}\ensuremath{\rightarrow}10s^{2}S_{1∕2}$ double-resonance transition in the presence of Ar. Satisfaction of double-resonance condition, achieved by use of a two-photon two-color pulse laser excitation scheme, was monitored by measurement of the intensity of the $9p^{2}P_{1∕2}\ensuremath{\rightarrow}6s^{2}S_{1∕2}$ cascade fluorescence at
361.73nm. In the experiment anisotropies, namely, alignment and orientation in the
6p2P3∕2 level, were produced from circularly polarized light with positive helicity. Then, a circular polarization degree was measured when both lasers were circularly polarized with positive helicities, and alternately positive and negative helicities for the $6p^{2}P_{3∕2}\ensuremath{\rightarrow}10s^{2}S_{1∕2}$ transition. From the measurement, we obtained the orientation-dependent depolarization cross section in the
6p2P3∕2 level due to collisions with ground-level argon atoms. A disorientation cross section value of 151
(42)A˚2 is reported.