Resonant low-energy electron attachment to O\(_{2}\) impurities in dense neon gas

TL;DR

This study investigates resonant low-energy electron attachment to O₂ impurities in dense neon gas across various temperatures, revealing density-dependent peaks linked to vibrational states and explaining the phenomena with an ionic bubble model.

Contribution

It provides the first detailed analysis of vibrational resonance peaks in electron attachment to O₂ in neon, incorporating temperature effects and a theoretical ionic bubble model.

Findings

Resonant peaks correspond to vibrational levels of O₂⁻ ions.

A second peak appears at higher density for lower temperatures.

The peak shape is explained by electron energy shifts and density of states.

Abstract

We report measurements of resonant low-energy electron attachment to O\(_2\) molecular impurities in neon gas in the temperature range \(46.5\,\mbox{K}\le T\le 101\,\mbox{K}\). The reduced attachment frequency \(\nu_A/N\) shows a well defined peak as a function of the gas density \(N\) when the electron energy is resonant with the 4th vibrational level of O\(_2^-\). For \(46.5\,\mbox{K}\le T\le 48.4\,\)K a second peak has been detected at a much higher density, which is due to the formation of ions in the 5th vibrational level. The temperature dependence of the first peak position can be explained within an ionic bubble model by computing the electron excess free energy as a function of \(T\) and \(N\). The peak shape is rationalized by taking into account the density dependent shift of the electron energy distribution function and the density of states of excess electrons in a disordered medium, and by assuming that electrons sample the gas density over a region of the order of the ionic bubble radius.