Ab initio study of the electronic structure of AlP-and electron affinity of AlP

The potential curves of 13 states of AlP - have been investigated using highly correlated CI wavefunctions and extended basis sets. The ground state is X 2 Sigma + (9 sigma 3 pi 4 ), followed closely (0.08 eV) by 1 2 Pi (3 pi to 9 sigma ). The states 1 4 Sigma + , 1 4 Delta , 1 4 Sigma - (3 pi to 4 pi ) and 1 4 Pi (3 pi 2 to 9 sigma 4 pi ) lie from 1.44 to 2.02 eV higher. The 2 2 Sigma + state (T e =1.71 eV) has a 8 sigma to 9 sigma configuration at short distances but a 3 pi to 4 pi structure for R>4.5 a 0 . Other doublet states arise from the same configurations as the corresponding lower-lying quartet states. Since no less than seven stable states of AlP - lie below neutral AlP, a photodetachment investigation of this anion represents a challenge to experimentalists. Other properties investigated are the dipole moments of X 2 Sigma + and 1 2 Pi , the ground-state dissociation energy and Franck-Condon factors for optical and electron detachment transitions.