Shape resonances in molecular photoionization

Abstract

Full text: Shape resonances have begun to play a central role in the study of spectroscopy and dynamics of molecular photoionization. They manifest themselves as bands of enhanced absorption in the spectra of most (nonhydride) molecules and often stand out prominently against a nonresonant background. These resonances arise from centrifugal barriers in the molecular potential experienced by the escaping photoelectron, and their gross features can be described in terms of simple barrier-penetration concepts. Using both experimental data and recent theoretical calculations, we survey the properties (e.g., symmetry, spatial distribution, and dominant partial waves) of several molecular shape resonances and show how this information relates to the analysis of wavelength-dependent photoelectron spectra, photoelectron angular distributions, and photoabsorption spectra of molecules in different physical states. Special emphasis will be given to the correspondence between resonances in molecular photoionization and electron-molecule scattering.