ABINITIO PREDICTION OF FUNDAMENTAL, OVERTONE AND COMBINATION BAND INFRARED INTENSITIES

Programs have been implemented for calculating ab initio anharmonic force fields which are quartic in displacement coordinates and, likewise, dipole-moment expansions which are cubic in displacement coordinates. Knowledge of these, and the use of second-order perturbation theory, leads to predictions for fundamental, overtone and combination band infrared intensities as well as the usual spectroscopic constants. Here we use the ab initio MP2 method, with large basis sets, applied to H2O and H2CO. The results, including those for the overtone and combination band intensities, are in good agreement with the available experimental data. © 1990.