Vibronic effects in the photon energy‐dependent photoelectron spectra of the CH3CN− dipole‐bound anion

摘要: Photoelectron spectra are reported for the ‘‘dipole‐bound’’ CH3CN− negative ion at three photodetachment energies (1.165, 2.331, and 3.496 eV), where anion is prepared by photodissociation of I−⋅CH3CN ion–molecule complex. While all dominated a single feature centered near zero electron binding energy, as expected dipole‐bound anion, vibrational structure also observed found to depend strongly on energy. This observation indicates that excitation not exclusively due distortion between neutral, but involves non‐‘‘Franck–Condon’’ effects. The origin energy dependence traced πCN* shape resonance corresponding valence or ‘‘chemical’’ anion. envelope nonresonant spectrum surprisingly similar infrared neutral acetonitrile, suggesting even this may result from intramolecular distortions. We develop simple mode...