Absolute Line Intensities for the ν6Band of H2O2

Abstract

The purpose of this work was to obtain reliable absolute intensities for the ν6band of H2O2. It was undertaken because strong discrepancies exist between the different ν6band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas,J. Mol. Spectrosc.1995. 171, 358), (R. May,J. Quant. Radiat. Transfer1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the ν6absorptions of H2O2. Consequently, Fourier transform spectra of H2O2were recorded at Giessen in a spectral range (370–1270 cm−1) which covers both theRbranch of the torsion–rotation band and thePbranch of the ν6band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion–rotation band with intensities computed using the permanent H2O2dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput,J. Mol. Spectrosc.1996. 176, 287–296) and [E. A. Cohen and H. M. Pickett,J. Mol. Spectrosc.1981. 87, 582–583). In the high frequency range, this value of the partial pressure of H2O2was used to measure absolute line intensities in the ν6band. Finally, the line intensities in the ν6band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the ν6band was generated, leading to a total band intensity of 0.185 × 10−16cm−1/(molecule.cm−2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams.