Ab initio characterization of the aluminum dimer in its X3Πu and A3∑g− electronic states

Abstract

The potential energy functions of the aluminum dimer, Al2, in its lowest‐energy electronic states, X 3Πu and A 3∑g−, have been determined from ab initio calculations using the multi‐reference averaged coupled‐pair functional method in conjunction with the correlation‐consistent basis sets up to septuple‐zeta quality. The core‐electron correlation, scalar relativistic, and spin‐orbit effects were taken into account. The vibration‐rotation energy levels for both the states of Al2 were calculated to near the “spectroscopic” accuracy. The 3Πu state was unequivocally confirmed to be the electronic ground state of Al2, and the electronic term value T0 of the 3∑g− state was predicted to be 247 cm−1. The energies and intensities of direct electronic‐vibration transitions X 3Πu ↔ A 3∑g− were predicted.