Collisional disorientation cross section in the J=1/2 cesium atoms*

Measurements of collisional depolarization cross sections play important role to gain valuable information about the interaction between neutral and rare-gas atoms. A key element to understand collision dynamics is the detail analysis of the polarization of the emitted photons. We have experimentally investigated collisional cross section of the excited $J$=1/2 cesium atoms, by collisions with the ground level argon atoms from a circular polarization spectra. Orientation in the $J$=1/2 level was optically induced by a circularly polarized light with a positive helicity. A two-photon double-resonance $6s\,^2S_{1/2}$$\rightarrow$$6p\,^2P_{1/2}$$\rightarrow10s\,^2S_{1/2}$ condition was achieved using nanosecond pulse dye lasers, and an intensity of the cascade fluorescence was monitored in the presence of argon atoms ranging from 5 mbar to 133 mbar. We present collisional disorientation cross section which was extracted from the circular polarization spectra.