Relaxation of atomic state multipoles by radiation re-absorption: Neon 2p2 atoms in a discharge plasma

In a positive column of a glow discharge in the magnetic field of 36.4 G, a linearly polarized laser pulse or a circularly polarized laser pulse has produced polarized neon atoms (alignment or orientation) in the 2p2 (Paschen notation) level from the 1s3 level. The subsequent fluorescence to the 1s2 level was observed with its polarized components resolved. Depopulation, disorientation and disalignment rates of the 2p2 atom were measured and their discharge current dependences were examined for a discharge current from 0.4 to 2.0 mA. The degrees of radiation re-absorption, or the optical thickness, of the transition lines from the 2p2 level to the 1s2-1s5 levels were measured as functions of the discharge current. A Monte Carlo simulation was performed by which the depopulation, disorientation and disalignment rates by the radiation re-absorption for these transitions were determined. The calculated rates were compared with the observed ones and found to reproduce the their discharge current dependences. D'Yankonov and Perel's analytical expression for these rates was quantified from comparison with the Monte Carlo results.