NEGATIVE-ION ZERO ELECTRON KINETIC-ENERGY SPECTROSCOPY OF I-CENTER-DOT-CH3I

The negative ion zero electron kinetic energy (ZEKE) spectrum of I-.CH 3I is presented and discussed. In addition to the high-frequency vibra tional structure previously seen in the photoelectron spectrum (PES) o f I-.CH3I, the ZEKE spectrum reveals low-frequency vibrational structu re due to excitation in two van der Waals modes in the ground (X) stat e of the neutral I.CH3I complex. Of the two other excited states of th e neutral complex, the I state is not distinctly observed, and no vibr ational structure due to van der Waals motion is observed for the II s tate.