A.R. Lee

A unified view of the spin conservation rule for disparate collisional processes

Abstract High resolution translational energy spectroscopy has been applied to a number of collisional processes, involving energy loss, charge transfer, charge stripping and charge inversion reactions. The role of the spin conservation rule has been assessed over this range of reactions and been found to hold, playing a vital part in the interpretation of these collision processes. Instances where the rule might be expected to break down, because of spin-orbit coupling, have been investigated and examples shown. In circumstances where free electrons are produced, and the spin of the ejected electron is indeterminate, it has been shown that application of the rule can be meaningful. The unexpected observation of intense simultaneous reactions (not arising from double collisions) is illustrated for a number of cases, which could only be clearly rationalised on the basis of the application of the spin rule.

Translational energy spectroscopy of single-electron capture by C2+ ions in He, Ne and Ar

Abstract High resolution (0.3 eV at FWHM) translational energy spectroscopy has been employed to study single-electron capture by 4 keV C 2+ ions in collision with He, Ne and Ar atoms. Our results are generally in good agreement with previous measurements. Our spectra reveal an additional weak channel for C 2+ in He and two additional weak channels for C 2+ in Ne, not previously reported. One of these capture channels in Ne occurs at a relatively large endothermic energy change. Eight transitions are identified for the single-electron capture by C 2+ in Ar.

Single electron capture by C3+ ions in He, Ne and Ar

Abstract Translational energy spectra have been obtained for 6 keV C 2+ ions resulting from single-electron capture by 6 keV C 3+ ions in collision with He, Ne and Ar. Our data for He and Ne are in good agreement with previous measurements, while data for the Ar target have not appeared in the literature. The spectrum for C 3+ in Ar is complex and appears to contain many strong spectral features which involve capture with excitation of the target product ion in Ar + .

Triple-electron capture by fast-moving doubly charged ions in single collisions with xenon atoms

Abstract The results of an investigation of triple-electron capture by fast-moving (6 keV translational energy) O 2+ and Cl 2+ ions in single collisions with xenon atoms are reported. Although the negative-ion yields were low, repeated scanning and signal averaging gave spectra with acceptably high signal-to-noise ratios. Peaks in the spectra were observed which, from their energy spacings, were interpreted in terms of triple-electron-capture reactions in which projectile ions in their ground electronic states, in single collisions with xenon atoms, generated Xe 3+ ions in various electronic states.

Collisional excitation of the Comet-Tail system of CO+ [A2Πi-X2Σ+]

Abstract High-resolution translational energy spectroscopy (0.1 eV full width at half maximum) has been performed on 3-keV CO+ ions scattered off Ar, N2, O2, CO, and NO. Excitation of the Comet-Tail system [A2Πi ← X2Σ+] of CO+ is prominent in all the spectra. Characteristic singlet-triplet electronic transitions of the target molecules are also present with N2, O2, and CO as target gases.