A b i n i t i o calculations on the four lowest electronic states of AlF+ and AlCl+

Abstract

The potential energy curves of the two lowest 2Σ+ (X,B) and the two lowest 2Π (A,C) electronic states of the AlF+ and AlCl+ molecular ions have been calculated using highly correlated multireference configuration interaction (MR-CI) wave functions. It is found that both 2Σ+ states and the C 2Πr state are bound, whereas the A 2Πi state is repulsive. Electronic transition moment functions for all six pairs of states of both ions have also been calculated and used for evaluation of the radiative transition probabilities between bound vibrational states. The calculated charge distributions show that the X and C states are dominated by Coulombic attraction between a doubly charged positive aluminum and the singly charged negative halogen ion. The results provide a new assignment of the photoelectron spectra of the neutral AlF. They are also in good agreement with the recently observed optical B–X emission spectra of both molecular ions and C–X bands of AlCl+. The absence of C–X emission of AlF+ is most likely due to predissociation of the C 2Πr state by the repulsive A 2Πi state.