The energy spectrum of aluminium monoxide

Abstract

SCF calculations using an extended double-zeta basis set have been performed in order to obtain information about the energy spectrum of AlO. The variational calculations concerned six states of AlO and three states of AlO +. Correlation energy differences were estimated semiempirically to correct the single-configuration approximation. The predominant configurations of the observed states of AlO have been identified by using a comparison between the calculated and observed spectrostropic elements: term values, rotational, vibrational and spin—orbit constants, compatibility of observed systems. This has led us to deduce the probable locations of as yet unobserved states and to predict the wavelength of a number of transitions in which they are involved. The ground state of AlO + has been found to be stable but its symmetry ( 3Π or 1Σ +) could not be ascertained. Particular emphasis has been laid on a study of the (2π 3 6α 2 7α3π) configuration of the highest-lying observed states of AlO. D 2Σ + and E 2Δ j. It is suggested that the quartet levels of this configuration are responsible for the perturbations experimentallly found in C 2Πr. The predissociation observed for E 2Δ i is finally discussed in terms of avoided crossings of potential curves.