Yun Ding

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

The infrared spectra of PH3 molecule were recorded on a Bruker IFS 120HR Fourier transform spectrometer from 4000 to 9500 cm−1. The P–H stretching vibrational frequencies and intensities were derived from the experimental data. The Morse oscillator parameters De and α 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...

High-resolution Fourier-transform intra-cavity laser absorption spectroscopy : Application to 12C2H2 near 12300 cm-1

The capabilities of intra-cavity laser absorption spectroscopy associated with a high-resolution Fourier-transform spectrometer (FT-ICLAS) are investigated with a Ti:Sapphire laser. Weak absorption lines of atmospheric water were used to test the accuracy of absolute intensity measurements by FT-ICLAS leading to an excellent agreement (a few %) with the HITRAN data. The performances in terms of spectral resolution (0.028 cm � 1 ) and sensitivity (2� 10 � 9 cm � 1 ) are illustrated by the spectroscopic study of the overtone spectrum of 12 C2H2 between 12 250 and 12 400 cm � 1 which allowed for a significant improvement of recent cavity ring-down measurements. Among the three P–R bands rotationally analyzed, one is newly observed. The absolute intensity values of the bands are given. 2003 Elsevier Science B.V. All rights reserved.

Overtone spectrum and the Fermi resonance of the SiH chromophore in SiHCI3

The Fourier transform and Fourier transform intracavity laser absorption spectra of the gas phase SiHCl3 molecule were recorded from 1000 cm-1 up to 13 000 cm-1. The normal mode analysis is carried out to fit the observed band centres. The reduced Hamiltonian models in terms of normal and curvilinear internal coordinates are used to study the Fermi resonance between the SiH stretching and bending modes and analyse the observed band centres associated with the SiH chromophore. The resonance in the SiH chromophore is found not to be important due to the cancellation of the contributions from the kinetic and the potential coupling terms. Off-diagonal anharmonic constants between the SiH stretching and bending manifold and the molecular frame have been determined. The SiH chromophore vibrational intensities are also reported.

Calculation of the Si–H stretching–bending overtones in SiHCl3 employing ab initio potential energy and dipole moment surfaces

The Si–H stretching–bending overtones in SiHCl3 were investigated employing theoretically calculated potential energy surfaces (PES) and dipole moment surfaces (DMS). The coupled cluster method CCSD(T) was utilized to generate both one-dimensional (1D) and three-dimensional (3D) surfaces. An empirical 3D PES was also taken into consideration. The computed energy levels and band intensities agree reasonably well with observation for most of the bands. Comparison of CCSD(T) and density functional results for the very weak 2ν1 band shows that it is essential to calculate the DMS at a high level of quantum-chemical theory when cancellation of linear and quadratic contributions to the DMS is significant. The 3D ab initio PES yields more accurate band intensities than the empirical PES and therefore appears to be more realistic.

Absolute local mode vibrational band intensities of AsH3

The local mode vibrational absolute band intensities of AsH3 molecule were studied experimentally and theoretically. The stretching vibrational band intensities of AsH3 were derived from the infrared spectra recorded by a Bruker IFS 120 HR Fourier transform spectrometer. A three-dimensional As–H stretching dipole moment surface (DMS) was calculated by the density functional theory method. The DMS was used to calculate the absolute band intensities, which agreed well with the observed values. The inter-bond coupling terms in the DMS expansion are found to be essential in reproducing overtone and combination band intensities in the high-energy regions. 2002 Published by Elsevier Science B.V.