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Line Intensities in the Far-Infrared Spectrum of H2O2

1996; Elsevier BV; Volume: 176; Issue: 2 Linguagem: Inglês

10.1006/jmsp.1996.0089

1096-083X

A. Perrin, J.‐M. Flaud, C. Camy‐Peyret, Roland Schermaul, Manfred Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, Jacek Koput,

Advanced Chemical Physics Studies

Using high resolution Fourier transform spectra (resolution 0.002 cm−1) recorded at the Instituto Ricerca Onde Electromagnetiche Firenze and at the Justus Liebig University Giessen, it has been possible to measure the relative intensities of lines in the far-infrared spectrum of H2O2in the 25–400 cm−1spectral region. These intensities were used as input data in a least-squares fit calculation in order to obtain the expansion parameters of the transition moment operator of the pure torsional–rotational transitions of H2O2. For these intensity calculations, the theoretical model takes into account the cos γ-type dependence of the dipole moment due to the large amplitude motion of the H atoms relative to the O–O bond, where 2γ is the torsion angle. The value of the dipole moment obtained from the fit of the observed intensities was then scaled to the value obtained from Stark effect measurements. Finally, a synthetic spectrum of the far infrared band of H2O2was generated, using the dipole moment expansion determined in this work for the line intensities and the parameters and the Hamiltonian matrix given in a previous analysis (C. Camy-Peyret, J.-M. Flaud, J. W. C. Johns, and M. Noel,J. Mol. Spectrosc.155,84–104 (1992)) for the line positions. In addition to the (Δn= ±1, ΔKa= ∓2) torsional–rotational resonances within the ground vibrational state, which are usually observed for H2O2, the Hamiltonian model takes explicitly into account both the vibration–rotation resonances involving the ground state and thev3= 1 vibrational state and the “staggering” effect which is due to thecispotential barrier.