title: Communication: photoelectron angular distributions of CH(-) reveal a temporary anion state.
abstract: Photoelectron imaging has broadened the scope of traditional photoelectron spectroscopy by combining a simultaneous photoelectron angular distribution, PAD, measurement with kinetic energy analysis. A fundamental understanding of PADs has been largely limited to simple atomic systems. However, a new model has recently been developed that predicts PADs as a function of electron kinetic energy for a simple linear combination of s and p atomic orbitals. We used CH(-) to test this model by acquiring PADs in a photoelectron imaging spectrometer at wavelengths from 600 to 355 nm. The PADs for electron detachment from the HOMO (1π) of CH(-) fit model predictions. However, the PADs associated with detachment from the HOMO-1 (3σ) orbital exhibit anomalous behavior at low electron kinetic energies because of a resonant process that arises from a previously undetected excited state of CH(-).
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Biswajit
authors.initials: B
authors.lastname: Bandyopadhyay
authors.forename: Carrie Jo M
authors.initials: CJ
authors.lastname: Pruitt
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Goebbert