The stretching vibrational overtone spectra of PH_3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities

摘要

The infrared spectra of PH3 molecule were recorded on a Broker IPS 120HR Fourier transform spectrometer from 4000 to 9500 cm-l. The P-H stretching vibrationalfr~uencies and intensities were derived!rom the experimental data. The Morse oscillator parameters D e and a in the anharmonically coupled anharmonic oscillator local mode model were determined by the .1east-squares fitting with the observed vibrational band centers. The ab initio three-dimensional P-H stretching dipole moment surfaces were calculated by the density functional theory method. The dipole moment vectors were projected to three kinds of molecule-fixed reference systems. The corresponding dipole moment components were fitted to polynomial functions in terms of the P-H bond length displacements with the molecular symmetry taken into account. The absolute band intensities were obtained and then compared with the experimental data. The results showed that a proposed improved bond dipole model can predict the absolute band intensities within a factor of 2 for most of the observed transitions, indicating a reasonably good agreement.