NEGATIVE-ION FORMATION FROM CH3I BY ELECTRON-IMPACT

The formation of fragment negative ions from CH3I on low energy electr on collision (0-50 eV) has been measured using a pulsed electron beam and pulsed ion extraction setup in a crossed-beam geometry. In additio n to I- we have observed H- and CH- at specific resonant energies due to dissociative electron attachment to CH3I. The cross-sections were p ut on an absolute scale using the relative flow technique. We have als o carried out ab initio molecular orbital calculations to derive infor mation on the ground state potential energy surfaces of CH3I, CH3I- an d their various dissociation products.