Absolute total cross sections for electron detachment and H-(D-) production have been measured for collisions of 0-and S-with H2 and D2 for relative collision energies ranging from approximately 0.5 to 25 eV. Electron detachment appears to occur via several mechanisms. Isotope effects are observed in all cross sections. Threshold studies indicate that there is no appreciable potential barrier to Hformation via the ion-molecule reaction 0-+ H2 ---+ H-+ OH, whereas a barrier of about 1 eV is observed for H-production in collisions ofS-with H 2 ·

Measurements of electron detachment cross sections, reactive charge transfer, and differential elastic and inelastic scattering cross sections for Cl−, Br−, and I− ions on CH3I, CH3Br, and CH3Cl targets are reported. The energy range for the experiments is from 3 to 150 eV. Of the very large number of reaction channels open, it appears that most make significant contributions to the total cross section for sufficiently high projectile energies. The SN2 reaction, which may be dominant at lower energies, was not observed and is probably not significant above the lowest energies in this study. Surviving primary ions exhibit a broad spectrum of inelastic loss, suggesting target breakup.

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