Abstract
This paper describes a semiempirical quantitative theory of the low‐lying electronic states of the radicals PH and PH2. The method is an extension of that developed by Jordan and Longuet‐Higgins to treat Row II hydrides. It indicates that a small percentage of d character in the valence state may have a considerable effect on the equilibrium bond angle, if the d orbital is somewhat contracted by polarization. Including this effect, the results are in excellent agreement with experiment: PH2 in its excited 2A1 state is found to be strongly bent; PH3 is predicted to have an inversion barrier of 34.5 kcal/mole.