Diffusion, De-excitation, and Three-Body Collision Coefficients for Excited Neon Atoms

Diffusion coefficients, de-excitation cross sections, and three-body collision coefficients for neon atoms of the 1s²2s²2p⁵3s configuration are obtained from optical absorption measurements of relative decay rates and relative densities of excited atoms following a pulsed discharge. Atoms in the lower metastable (³P₂) and the lower radiating (³P₁) states are destroyed by diffusion to the wall, three-body collisions involving two ground state atoms, and the escape of imprisoned resonance radiation. The diffusion coefficient at unit neon density and 300^∘{}K for the metastable states is 5.5×{}10¹⁸ cm^-1 sec^-1. The rate of escape of resonance radiation agrees with the predictions of Holstein's theory. At 300^∘{}K the average cross section for collisional de-excitation of ³P₁ atoms to the ³P₂ state is 5×{}10^-19 cm² and is about 6×{}10^-20 cm² for the ³P₀ to ³P₁ and ³P₀ to ³P₂ transitions. The cross section for the ³P₁ to ³P₂ de-excitation increases by an order of magnitude between 200^∘{}K and 500^∘{}K and is three times larger for de-excitation by helium than by neon at 300^∘{}K. The three-body collision coefficient for the ³P₂ state is 5×{}10^-34 cm⁶/sec at 300^∘{}K and 5×{}10^-35 cm⁶/sec at 77^∘{}K. Estimates of average cross sections for de-excitation by thermal electrons give 10^-13 cm² for the ³P₁ to ³P₂ process and 10^-14 cm² for the ³P₀ to ³P₁ transition.