Electric properties of the oxonium ion in its ground and two lowest excited states

The electric dipole moments and dipole polarizabilities of the oxonium ion have been calculated for the ground and two lowest excited states from the CASSCF and CASPT2 approaches. Two basis sets - an extended ANO and a smaller segmented basis - have been compared. The best values obtained at the CASPT2 level are mu = -0.5878 au (calculated at the centre of the nuclear charges), alpha(perpendicular to) = 6.93 an and alpha(parallel to) = 5.56 au for the ground state, alpha(perpendicular to) = 47.1 au and alpha(parallel to) = 10.8 au for the (1)A ''(2) excited state, alpha(perpendicular to) = 45.9 au and alpha(parallel to) = 11.5 an for the (3)A ''(2) excited state. To our knowledge, these are the first values available in the literature for the excited states.