Absolute line intensities for the nu(6) band of H2O2

The purpose of this work was to obtain reliable absolute intensities for th e nu(6) band of H2O2. It was undertaken because strong discrepancies exist between the different nu(6) band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Areas, J. Mol. Spectrosc. 1995. 171, 358), (R . Mg, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to meas ure simultaneously the far-infrared absorptions and the nu(6) absorptions o f H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Gi essen in a spectral range (370-1270 cm(-1)) which covers both the R branch of the torsion-rotation band and the P branch of the nu(6) band which appea r at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of th e spectra was determined by calibrating the observed absorptions in the tor sion-rotation band with intensities computed using the permanent H2O2 dipol e moment measured by Stark effect (A. Perrin, J.-M. maud, C. Camy-Peyret, R . Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Kopu t, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Picket t, J. Mol. Spectrosc. 1981. 87; 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line in tensities in the nu(6) band. Finally, the line intensities in the nu(6) ban d were fitted using the theoretical methods described in detail in our prev ious works. Using these new results on line intensities together with the l ine position parameters that we obtained previously, a new synthetic spectr a of the nu(6) band was generated, leading to a total band intensity of 0.1 85 x 10(-16) cm(-1)/(molecule.cm(-2)) at 296 K. It has to be pointed out th at the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. (C) 1999 Academic Press.