Angular and energy distributions of electrons from 7.5–150-keV proton collisions with oxygen and carbon dioxide

Abstract

Cross sections for the ejection of electrons, differential in the angle and energy of emission, were measured for proton collisions with two molecular gases, oxygen and carbon dioxide, over the primary energy range of 7.5-150 keV and an angular range of 10" to 160". The energy distributions, obtained by integration over the angle, were fitted by an analytical model. A discrepancy in the angular distributions compared to those of Gibson and Reid

Electron production in proton collisions with atoms and molecules: energy distributions

“…In general, their numbers can be shown to be negligible (Cheng et al, 1989b). Photons created in the target by the incident beams, however, are a demonstrably serious source of background, and have been observed by Rudd et al (1966).…”

“…This problem is not discussed by any of the researchers using gas-beam targets except Gibson and Reid and may be a source of significant error. In this regard, we mention the systematic differences in the measured angular dependence of doubly-differential cross sections between Gibson and Reid and other workers (see, specifically, Reid, 1986, andCheng et al, 1989b). It appears that the poorly characterized shape of the effusive gas target in Gibson and Reid's "fountain" spectrometer allows a significant angular dependence of (nlfl),f that was not accounted for in the analysis.…”

“…The Nebraska group coated their chamber walls with colloidal graphite and added baffles to impede scattered electrons. These precautions produced no significant differences from previous data Cheng et al, 1989b). The Pacific Northwest Laboratories group crumpled fine wire mesh and inserted it directly behind the proton beam in their target cell to prevent reflected electrons from leaving the cell (see Fig.…”

“…The first, used by Rudd and co-workers (e.g., Rudd and Jorgensen, 1963;Rudd et al, 1966;Crooks and Rudd, 1971;Rudd and Madison, 1976;Criswell et al, 1977;Bolorizadeh and Rudd, 1986;Cheng et al, 1989aCheng et al, , 1989b, involves filling a relatively large volume with a uniform pressure of target gas. The gas is contained in a cylindrical chamber whose only openings are an entrance port for the proton beam and an exit aperture placed at one of several angles for the ejected electrons (Fig.…”

Energy and angular distributions of electrons from ion impact on atomic and molecular hydrogen. I. 20–114-keVH++H2Gealy1, Kerby2, Hsu3 et al. 1995Phys. Rev. ASelf Cite358161View full textAdd to dashboardCite

“…The single measurement at 50 keV of Gibson and Reid [5] covered angles down to 0" but only up to 100" and therefore gives little information about eiection of electrons into the backward hemisphere. Furthermore, the accuracy of their angular distributions was brought into question by Cheng, Rudd, and Hsu [6]. Rudd and Jorgensen [7] presented data only at 100 keV.…”