Electron Detachment Cross Sections Research Articles

Scattering of Low-Energy H— Ions in Helium, Neon, and Argon

Elastic and inelastic cross sections have been measured for the scattering of H— ions in helium, neon, and argon gases, at incident ion energies in the range 5 ev to 350 ev. One term interaction potentials of the form V=—K/rn were calculated from the low-energy elastic cross sections. These potentials were: for H— and He, V=—2.90/r3.01 ev for r=1.30 A to 1.90 A; for H— and Ne, V=—4.17/r2.80 ev for r=1.00 A to 1.78 A; and for H— and A, V=—7.82/r3.40 ev for r=1.23 A to 2.12 A. The observed inelastic cross sections are interpreted as cross sections for electron detachment from H—; they show a similar behavior with ion energy W in the three cases, appearing at W between 0 and 5 ev, rising rapidly to W=40 ev, and then rising very slowly to W=350 ev. Evidence was found for positive ion formation in H— collisions with Ne and A atoms at ion energies above 100 ev.

Charge Exchange Cross Sections of Hydrogen Ions in Gases

Measurements are reported of the cross section for electron capture (${\ensuremath{\sigma}}_{10}$), electron loss (${\ensuremath{\sigma}}_{01}$), and electron detachment (${\ensuremath{\sigma}}_{\ensuremath{-}10}$) for hydrogen atoms and ions traversing several gases. (${\ensuremath{\sigma}}_{\mathrm{if}}$ represents the cross section for charge transfer from initial state $i$ to final state $f$.) The kinetic energy of the particle was from 3 kev to 200 kev. The target gases used were ${\mathrm{H}}_{2}$, He, ${\mathrm{N}}_{2}$, ${\mathrm{O}}_{2}$, Ne, and A. Cross sections were determined by measuring the attenuation of the hydrogen beam in a gas cell under the influence of an electrostatic or magnetic field. The fraction of the beam in each charge state after passing through a "thick target" was also determined. This latter measurement served as a test for internal consistency of the data, since the fraction is relatable to the cross section for entry to and exit from the charge state. The loss cross section, ${\ensuremath{\sigma}}_{01}$, increased monotonically at low energies, reaching a maximum at a velocity approximately equal to the orbital electron velocity. For the higher energies studied the capture cross section could be represented by an expression of the form, $\ensuremath{\sigma}=A{e}^{\ensuremath{-}bv}$, where $A$ and $b$ are constants for each gas studied. The electron attachment cross section, ${\ensuremath{\sigma}}_{0\ensuremath{-}1}$, was of the order ${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$/gas atom for the gases studied and attained a maximum between 5 and 20 kev. The inverse transition, ${\ensuremath{\sigma}}_{\ensuremath{-}10}$, was approximately ${10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{2}$/gas atom in the energy range studied.

Further investigations of charge exchange and electron detachment - I. Ion energies 3 to 40 keV - II. Ion energies 100 to 4000 eV

This paper describes the measurement of charge transfer cross-sections for protons, molecular hydrogen ions and helium ions in the rare gases and hydrogen, and electron detachment cross-sections for negative atomic hydrogen ions in the rare gases. Part I describes the energy range 3 to 40 keV. In part II the energy range 100 to 4000 eV is described, and the results are discussed in terms of the pseudo-adiabatic hypothesis. Comparisons are made with other experimental results, and anomalous molecular cases are discussed in terms of reactions involving anti-bonding states.