I- CH₃ X (X=Cl,Br,I) photodetachment: The effect of electron-molecule interactions in cluster anion photodetachment spectra and angular distributions

The electron kinetic energy dependence of the photoelectron spectra and angular distributions of I- CH₃ X (X=Cl,Br,I) cluster anions are measured via velocity mapped imaging at wavelengths between 350 and 270 nm. Processes analogous to those encountered in free CH₃ X -electron interactions are revealed. In particular, the presence and energies of resonances associated with a low lying σ state have a marked effect on the results of I- CH₃ X photoexcitation. These effects (vibrational excitation, product anion production, and alteration of the photoelectron angular distribution) are far more prominent for I- CH₃ I. However, in the vicinity of the P2 1/2 threshold there is a sharp deviation in the P2 3/2 channel angular distribution and an enhancement of the P2 3/2 channel vibrational structure of all three cluster anions. These latter effects are specific to the cluster anion environment through the relaxation of the partner excited I atom and subsequent electronic autodetachment.