Cross sections for polarization relaxation of excited neon atoms by helium atom collisions: Disalignment and disorientation

T. Fujimoto, M. Hasuo, M. Nimura

Graduate School of Engineering
Kyoto University
Kyoto 606-8501
Japan

We have performed polarization-resolved LIF (laser-induced fluorescence) experiment on a mild glow discharge in a neon-helium mixture gas at temperatures of 14K - 300K. One of the neon 2p53p configuration levels is excited by a pulsed laser radiation. This laser light is linearly or circularly polarized. By observing the time-dependent direct fluorescence radiation with its polarized components resolved, we obtain a disalignment rate or a disorientation rate. By changing the helium atom pressure we obtain the rate coefficients. The results are compared with the theoretical rate coefficients. Both agree very well for temperatures higher than 77K. With a decrease in temperature the experimental rate coefficients decrease monotonically, while the theoretical rate coefficients deviate upward substantially. Our experiment suggests the absense of the resonance structure in the theoretical cross sections in the energy range of <5meV.