Photoionization of the neon–rare gas dimers near the neon 3s resonance transitions: A study of associative ionization half-reactions

Abstract

The relative photoionization cross sections of NeAr, NeKr, and NeXe are reported in the energy region of the first excited states of atomic neon, which includes the dipole‐allowed 3s[3/2]⁰₁ and 3s′[1/2]⁰₁ states and the dipole‐forbidden 3s[3/2]⁰₂ and 3s[1/2]⁰₀ states. All three molecular spectra show both a narrow band at approximately the position of the 3s′[1/2]⁰₁ atomic transition and a broader band blue shifted from this level. A similar, but much weaker, broad band is observed blue shifted from the 3s[3/2]⁰₁ atomic transition in NeAr. No molecular bands are observed near the dipole‐forbidden atomic neon states. The broad molecular band blue shifted from the 3s′[1/2]⁰₁ transition in all of the dimer spectra results from excitation to the repulsive wall of NeRg*, followed by rapid autoionization to form NeRg⁺, similar to the associative ionization reaction Ne*+Rg→NeRg⁺+e. The relative absorption cross sections for transitions to the discrete molecular state were calculated for each dimer using NeRg* excited state potential energy curves derived from metastable Ne*–rare gas scattering experiments. The relative photoionization cross sections were then estimated using the known energy dependence of the associative ionization cross sections, and the results are in good agreement with present observations.