Near threshold Cl~?·CH_3I photodetachment: Apparent ~2P_(1/2) channel suppression and enhanced ~2P_(3/2) channel vibrational excitation

摘要

Cl~?·CH_3I cluster anion photoelectron images are recorded over a range of detachment wavelengths in the immediate post threshold region. The photoelectron spectral features fall into two categories. A number of weak, photon energy dependent transitions are observed and attributed to atomic anion fragmentation products. Several more intense, higher electron binding energy transitions result from single photon cluster anion detachment. Comparison with I~?·CH_3I suggests that the detachment process is more complicated for Cl~?·CH_3I. The single photon transition spacing is consistent with CH_3I ν_3 mode excitation, but the two distinct vibronic bands of I~?·CH_3I detachment are not easily distinguished in the Cl~?·CH_3I spectra. Similarly, while the spectral intensities for both cluster anions show non-Franck Condon behavior, the level of vibrational excitation appears greater for Cl~?·CH_3I detachment. These observations are discussed in terms of low lying electronic states of CH_3I along the C-I coordinate, and the influence of the CH_3I moiety on the neutral halogen atom states.