A PERTURBATION METHOD FOR CALCULATING VIBRATIONAL DYNAMIC DIPOLE POLARIZABILITIES AND HYPERPOLARIZABILITIES

Perturbation formulas are derived for calculating the vibrational dynamic polarizability (alpha-upsilon) and hyperpolarizabilities (beta-upsilon and gamma-upsilon) of polyatomic molecules. These formulas, based on an initial harmonic oscillator approximation, include corrections for mechanical anharmonicity (cubic) terms in the vibrational potential and electrical anharmonicity (quadratic) terms in the dependence of the electrical field polarization potential on nuclear coordinates. Results are presented for FH and CO2. In the former case, comparison is made to "exact" numerical values. Fully documented computer programs for the perturbation treatment are available.