Computational study of the spectroscopic constants of the ground state of the As2 molecule

Spectroscopic constants of the ground state of the As2 molecule have been evaluated using a series of complete active space self-consistent-field and second-order configuration interaction calculations with all-electron basis sets. Angular correlation is found to contribute significantly to the dissociation energy. The calculation with a set of [8s6p4d2f1g] basis functions gives 3.58 eV for the dissociation energy, in contrast to the experimental value of 3.99 eV.