Electronic states of Al 2

Abstract

Ab initio multi-configuration self-consistent field and first-order configuration interaction (FOCI) calculations in an extended basis set have been carried out for the lower energy electronic states of Al 2. The ten core electrons of each Al atom were replaced by an accurate compact effective core potential. The FOCI calculated T o value for the 3Σ g −- 3Σ u − transition agrees with the experimentally observed emission band to within 90 cm −1. 3Π u is calculated to be the electronic ground state of Al 2. Based on FOCI energies and qualitative intensity arguments, the reported optical absorption spectrum of matrix isolated Al 2 also agrees best with a 3Π u ground state. The 3Σ g −1 state is calculated ( T e) at only 324 cm −1 above the 3Π u state, and the 1ΣE g + state is predicted to lie higher.