Perturber dependence of disalignment cross sections of the argon 2p ₂ atoms measured at temperatures between 77 and 295K

In a temperature controlled glow gaseous discharge of pure argon, or a mixture of argon and helium or neon at 77, 135, 190, 240, and 295 K, a linearly polarized laser pulse produces polarized argon atoms on the 2p ₂ (in Paschen notation) level from the 1s ₃ level. We measure the direct fluorescence from the 2p ₂ level to the 1s ₂ level with its polarization components resolved. From the temporal evolution of the intensities for these components, we determine the disalignment rate. We also determine the disalignment rate coefficients due to helium, neon and argon atom collisions by separating the effect of radiation reabsorption, and then determine the effective cross section of disalignment from the rate coefficient divided by the mean relative velocity of colliding atoms. It is found that perturber rare gas atoms with larger atomic number have larger depolarization cross section. This effect can be attributed to larger values of the dipole polarizability for perturbers with larger atomic number.