Experimental Determinations of Charge Transfer Cross Sections and Secondary Electron Emission by Ion Bombardment

Abstract

The method utilized by the authors for determining charge transfer cross sections has been improved and applied to symmetric and unsymmetric reactions involving the inert gases, N2, H2, CH4, C2H4, C2H6, and C3H8. The cross sections were found to be about 20% higher than the values previously reported. The discrepancy can be explained by the fact that in previous experiments cross sections were determined from net charge measurements without taking full account of the secondary electrons impinging on the plate where the charge transfer ions were collected. As expected from adiabatic hypothesis, the reactions involving mixtures of gases having nearly equal ionization potentials were found to have maximum cross sections for low-energy ions. The interaction distances were calculated from the observed ion energy for which the cross sections are a maximum. The method described here can be utilized to determine the secondary electron emission from a metal surface due to ion bombardment. Such determination has been made for a brass surface. Relating the variation of emission with the ion mass and energy, it is found that the emission varies inversely as the square root of the ion mass.

Cold-cathode discharges and breakdown in argon: surface and gas phase production of secondary electrons

“…In spite of the uncertainties, these results are consistent with more recent data. Recently, Böhm and Perrin [78] •, Cu, [75]; ♦, , Cu, [45]; , , Ta, [80]; ×, W, [79]; , brass, [81]; •, unknown, [50] and , CuBe, [51]. The solid curves are plots of the analytical yield expressions for dirty surfaces for Ar + and Ar, while the dashed curves are the representative yield curves for clean surfaces for Ar + ions and Ar atoms from figure 1.…”

“…The measurements for Ar + (open points) in figure 2 show that for low energies (<150 eV) there is more than a two order of magnitude spread in the yields. Some of the low-energy data [45,81] show relatively large yields, such as those observed on exposure of the metal [68,69] to gases like H 2 , N 2 and CO, while data [50,69,79] obtained following exposure to O 2 or H 2 O show very small yields. Much of the Ar + data at energies below 100 eV suggest the relatively weak dependence on ion energy characteristic of potential (Auger) [37,42,43,68] ejection.…”

Electron capture and dissociation of the molecule in slow collisions

“…Most of the investigations of charge exchange between ions and molecular nitrogen have dealt with singly and doubly charged ions [1][2][3][4][5][6][7][8][9][10][11][12][13][14] at projectile energies from 1 eV up to several MeV. Up to now, few authors have investigated electron capture reactions involving multiply charged ions and molecular nitrogen.…”