p-wave photodetachment in a static electric field

Photodetachment from negative ions initially bound in s states has been studied in a static electric field. A 10-keV ion beam was sent through a region with fields of up to 1.5 kV/cm applied parallel to the beam direction. A pulsed dye-laser beam, perpendicular to the ion beam, photodetached the ions. The relative cross sections were measured by detecting the resulting fast neutral atoms with a gated channeltron detector. Polarization-dependent electric-field oscillations were oberved on the p-wave detachment cross section of Au^- near the threshold at 18 620.2 cm^-1. A simple theory for calculating the oscillatory structure is presented. Good agreement is found between the data and the theory, for laser polarizations both parallel to and perpendicular to the static electric field.