Negative-ion photodetachment in a weak magnetic field

A sequence of three frame transformations is used to describe the escape of a photoelectron into a uniform magnetic field. Standard elements of quantum-defect theory are combined with a Harmin-Fano-type local frame transformation from spherical to cylindrical coordinates, accounting nonperturbatively for the electron motion in both the magnetic field and the field of the atom. A dramatic dependence of the cross section on the incident light polarization is predicted whenever s waves are not present at threshold, as in ${\mathrm{H}}^{\mathrm{-}}$ photodetachment.