a Bond Selective Chemistry, University of Science and Technology of China, Hefei 230026, China; b Department of Basic Education for Information, Anhui College of Traditional Chinese Medicine, Hefei 230038, China
Abstract The overtone spectra of H2SiCl2 molecule in the regions of 2000—9000cm-1 and 12000—12900cm-1 at room temperatures have been studied by use of high-resolution Fourier transform spectroscopy and sensitive-intracavity-laser absorption spectroscopy, respectively. The variations of vibrational quantum numbers ΔVSiH=1, 2, 3, 4 and 6 for the overtones of the SiH stretching have been analysed and assigned with the local mode model and the normal mode model. The values of harmonic frequency $\omega$m, anharmonicity constant $\chi$m, bond coupling constant $\lambda$, the Morse oscillator parameters De, $\alpha$, and interaction force constant frr′ are derived from the experimental spectrum with nonlinear least-squares fitting. The most striking feature of the SiH2Cl2 is that the larger the vibrational energy, the smaller the energy difference between a couple of lowest stretching states of a given manifold, and finally, the couple of lowest stretching states are degenerated within the experimental error for ΔVSiH≥4 vibrational manifolds. The degenerate energy level structure resembles that of a diatomic Morse oscillator; the transition energies show a remarkable fit to the Birge—Sponer relation. The high vibrational states can be described straightforward with a SiH diatomic Morse oscillator wavefunction, this is an indication of vibrational bond localization.
Received: 04 September 2003
Revised: 02 November 2004
Accepted manuscript online:
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