Theory of Threshold Energy Dependence of Photodetachment of Diatomic Molecular Negative Ions

The energy dependence near zero energy of the continuum wave function of an electron in a molecular potential field is found by an iterative solution of the wave equation. This leads to shapes for the photodetachment cross section near threshold which are found to depend on whether the molecular ion is heteronuclear or homonuclear and on the $u$, $g$ symmetry (for homonuclear case) of the outer molecular orbital. The predicted energy dependences are found to be consistent with the available experimental data.