Photoemission Cross Sections for Atomic Transitions in the Extreme Ultraviolet due to Electron Collisions with Atoms and Molecules

Abstract

This article reviews experimental photoemission cross sections in the extreme ultraviolet, for transitions in excited atoms and atomic ions formed in electron collisions with atoms and molecules. A survey of the available experimental data for each investigated target gas reveals severe inconsistencies between cross sections reported by different laboratories. As almost all reported cross sections are based on relative measurements, a detailed discussion is given of the methods used for normalization of the cross sections.

Proton and electron impact on molecular and atomic oxygen: I. High resolution fluorescence spectra in the visible and VUV spectral range and emission cross-sections for dissociative ionisation and excitation of

“…Comparison of our emission cross-sections for 200 eV electron impact with the data from Ajello and Franklin [6] and from Morgan and Mentall [7]. Van der Burgt et al [22] by 10%, whereas those of Morgan and Mentall [7] decrease by nearly a factor of 2.…”

“…Van der Burgt et al [22] recommended a renormalisation of the emission cross-sections due to a new electron impact induced cross-section for the Lyman-α line emission from H 2 . The renormalisation is supported by the accurate emission cross-section measurement of Jans [20].…”

“…In consequence, the difference between emission cross-sections measured by ourselves and by Ajello and Franklin [6] cannot be attributed to the reference emission cross-section. A 92.0 nm line emission cross-section for 200 eV electron impact of Mentall and Morgan [27] was also renormalised by van der Burgt et al [22] yielding σ = 2.15 Mb. Extrapolation, employing the energy dependence of the experimental 92.0 nm line emission cross-sections of Luyken et al [31] (σ = 1.29 Mb at 2 keV), yields σ = 0.27 Mb at 2 keV.…”

Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

“…46 Of these atomic lines, the largest are the oxygen atom multiplet at 130.2-130.6 nm (2p 3 3s 3 S o ! 2p 43 P), with additional weaker lines at 98.9, 102.6, 103.9, and 135.8 nm.…”

“…X 1 R þ g ) in the 100-260 nm wavelength range, and portions of the second positive (2 P) system N 2 (C 3 P u ! B 3 P g ) (268-546 nm), first negative 28,46 Note that almost all of these emissions occur at wavelengths above the maximum range of the vacuum photodiode detector; and a majority of the molecular emissions are more properly classified as UV rather than VUV emissions.…”