The HeI excited electron spectrum of phosphine

Abstract
The HeI excited electron spectrum of phosphine (PH3) has been recorded with high resolution. The 2 A 1 band reveals an extensive vibrational progression in the v 2 bending mode with irregular structure at the low binding energy side due to hindered inversion. The existence of a barrier in the PH3 + 2 A 1 ionic state has been confirmed by vibrational energy level and Franck-Condon factor calculations based on CASSCF calculations of the total energy. The equilibrium angle between a P-H bond and the plane of the three hydrogen atoms in this ionic state was determined to be 15·5° and the barrier against inversion to be 160 meV. The adiabatic electron binding energy of this transition ([Xtilde] 2 A 1X 1 A 1) was found to be 9·868±0·005 eV.