A quantum chemical study of the infrared absorption intensities of the isoelectronic C 2v systems H 2F +, H 2O and NH −2

Abstract

The results of a comparative theoretical study of the dipole moment derivatives and infrared absorption intensities within the double harmonic approximation are presented for the isoelectronic, isostructural C 2v molecules: H 2F +, H 2O and NH − 2. The calculations, performed at the ab initio SCF and CI levels of theory, utilize basis sets of triple zeta+two polarization functions quality. For the ions H 2F + and NH − 2, in the absence of adequate experimental data the equilibrium geometries and force constants were also calculated. The trends observed in the dipole moment derivatives for the three systems are indicative of the amount of electronic charge associated with the hydrogen atoms and are very similar to the trends noted for a set of C 3v hydrides.