Measurements of partial cross sections and photoelectron angular distributions for the photodetachment of Fe⁻ and Cu⁻ at visible photon wavelengths

Photodetachment cross sections and the angular distributions of photoelectrons produced by the single-photon detachment of the transition metal negative ions Fe⁻ and Cu⁻ have been measured at four discrete photon wavelengths ranging from 457.9 to 647.1 nm (2.71–1.92 eV) using a crossed-beams laser photodetachment electron spectrometry (LPES) apparatus. Photodetachment cross sections were determined by comparing the photoelectron yields from the photodetachment of Fe⁻ to those of Cu⁻ and C⁻, which have known absolute photodetachment cross sections. Using the measured photodetachment cross sections, radiative electron attachment cross sections were calculated using the principle of detailed balance. Angular distributions were determined by measurements of laboratory frame, angle-, and energy-resolved photoelectrons as a function of the angle between the linear laser polarization vector and the momentum vector of the collected photoelectrons. Values of the asymmetry parameter have been determined by nonlinear least-squares fits to these angular distributions. The measured asymmetry parameters are compared to predictions of photodetachment models including Cooper and Zare’s dipole approximation theory [ J. Cooper and R. N. Zare J. Chem. Phys. 48 942 (1968)], and the angular momentum transfer theory developed by Fano and Dill [ Phys. Rev. A 6 185 (1972)].