The stretching vibrational overtone spectra of PH3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities

Abstract

The infrared spectra of PH 3 molecule were recorded on a Bruker IFS 120HR Fourier transform spectrometer from 4000 to 9500 cm Ϫ1 . The P-H stretching vibrational frequencies and intensities were derived from the experimental data. The Morse oscillator parameters D e and ␣ in the anharmonically coupled anharmonic oscillator local mode model were determined by the least-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.

Absolute local mode vibrational band intensities of AsH3

“…But it gives similar Table 3 Expansion coefficients a of the dipole moment surfaces of AsH 3 molecule results, which are not listed here. As mentioned in [17], the Eckart conditions are not crucial in studying this kind of problems -the stretching vibrational band intensities of XH 3 molecules (X ¼ P, As, Sb). In summary, in this work we study the absolute local mode vibrational band intensities of AsH 3 molecule experimentally and theoretically.…”

“…The procedure of calculating the 3D As-H stretching DMS of AsH 3 by the DFT method is similar to the one used for PH 3 in our earlier work [17]. The calculations were done by using GAUS-SIAN SIAN 98 package [19].…”

“…The optimized As-H bond length and H-As-H bond angle in equilibrium configuration are 1.5218 A A and 92.0474°, which agree well with the experimental values [23] 1.511060 (14) A A and 92.0690(14)°, respectively. The method of scanning the 3D DMS can be referred to [17].…”

“…This DMS model can be called the improved bond dipole model [17], which includes the inter-bond coupling terms. The expansion coefficients are fitted with the DFT calculated data points.…”

“…A three-dimensional (3D) As-H stretching dipole moment surface was calculated by density functional theory (DFT). This method has been successfully used to predict the absolute stretching vibrational band intensities of PH 3 [17].…”