Electron capture by trappedNeq+ions at very low energies

An electrostatic ion trap is used to trap ${\mathrm{Ne}}^{q+} \left(1\mathrm{}\le q\le 10\right)$ ions created by a fast xenon beam passing through neon gas. Decay of a given charge state during the trapping time is due to electron-capture collisions with the ambient gas. Measurement of the decay constant versus density yields a rate constant, from which an effective cross section is derived. ${\mathrm{Ne}}^{q+} + \mathrm{Ne} \mathrm{}(q=3-10\mathrm{})\mathrm{}$ and ${\mathrm{Ne}}^{q+}+\mathrm{Xe} \mathrm{}(q=6-10\mathrm{})\mathrm{}$ collisions have been studied at mean collision energies in the range 1.0-70.0 eV. Marked oscillation of the effective capture cross sections with charge at fixed mean collision energies is observed. A strong velocity dependence of the effective cross section (rising as the velocity decreases) is observed for several collision pairs.