Multiconfigurational quadratic response theory calculations of two-photon electronic transition probabilities of H₂O

Two-photon electronic probabilities for low-lying electronic states of H₂O are carried out using MCSCF quadratic response theory. Basis set dependency and electron correlation effects are investigated. The transition probabilities and polarization ratios for the first excited states of each symmetry have been calculated as a function of the laser frequencies. It is found that inclusion of the E[³] and S[³] terms in the response equations cannot be neglected for the description of the transition probabilities and polarization ratios. A comparison with previous theoretical studies is addressed.