Electron-impact detachment from PO{sub n}{sup -} (n=0-3)

Electron detachment from PO{sub n}{sup -} (n=0-3) by electron impact was studied for incident-electron energies in the range from 0 to 50 eV. In all cases, the cross section for electron detachment exhibits a well-defined onset at a threshold energy that is significantly higher than the electron binding energy. For P{sup -}, PO{sup -}, and PO{sub 2}{sup -}, the overall shape of the detachment cross section is represented fairly well by a classical model cross section. For PO{sub 3}{sup -}, however, deviations occur. It is suggested that deviations appear because the detachment process is dependent on the relative orientation of the molecular ion with respect to the incoming electron. For all the molecular ions studied here, the dominant reaction channel is pure detachment without fragmentation of the molecule. At higher energies, electron impact furthermore results in dissociative detachment where a P-O bond is broken. Three- and four-body fragmentation is found to be negligible.