Photodetachment cross sections of theC2nH− (n=1–3)hydrocarbon-chain anions

Abstract

We report theoretical results of the low-energy photodetachment cross sections of the ${\mathrm{C}}_{2}\mathrm{H}{}^{\ensuremath{-}},\phantom{\rule{0.16em}{0ex}}{\mathrm{C}}_{4}\mathrm{H}{}^{\ensuremath{-}}$, and ${\mathrm{C}}_{6}\mathrm{H}{}^{\ensuremath{-}}$ hydrocarbon-chain anions. The complex Kohn variational technique is used to calculate molecular-frame transition dipole moments from the anion ground state to a photoelectron in the continuum of the neutral radical. We employ the Franck-Condon approximation and include interchannel electronic coupling to determine the low-energy photodetachment cross sections and asymmetry parameters. We discuss the behavior of the cross section, especially near thresholds, and describe the role of electronic resonances and excited channels. The theoretical results reproduce the main characteristics of recent measurements of absolute photodetachment cross sections.