Laboratoire Of Physique Moleculaire

Tunis, Tunisia

Laboratoire Of Physique Moleculaire

Tunis, Tunisia

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Ben Mabrouk K.,Laboratoire Of Physique Moleculaire | Aroui H.,Laboratoire Of Physique Moleculaire | Orphal J.,University Paris Diderot | Orphal J.,Karlsruhe Institute of Technology
AIP Conference Proceedings | Year: 2010

Using Fourier Transform spectra (Bruker IFS 120 HR, resolution ≈ 0.004 cm-1) of NH3 in several branches of the v2, 2v2 and v4 bands, absolute line intensities have been determined at room temperature (T = 295 K) for more than 400 rovibrational lines located in the spectral range 1000-1800 cm-1. A non-linear least-squares multispectrum fitting procedure, including line mixing effects, has been used to retrieve the line intensities from eleven experimental spectra recorded at different pressures of pure ammonia. The present results are compared with previous measurements1,2,3 in which the collisional absorption coefficient is a Voigt profile. The line intensities determined in the present work are smaller than those determined by these authors. For example, the difference in percent between our values and the values of C. Cottaz1 is about 6%. For almost all lines and pressures considered in this work, it was shown that the first-order Rosenkranz absorption coefficient taking into account line-mixing effects is adequate to extract with sufficient accuracy the line intensities of NH3. An examination of these line intensities shows a pronounced J and K quantum numbers dependencies. Our results have been analyzed to obtain effective transition moments and correction parameters of symmetric and asymmetric partial bands of the fundamental v 4 band, as well as those of asymmetric partial bands of v2 and 2v2 bands. Since these bands are affected by the rotation-vibration interactions, the zero-order theory where the Hermann-Wallis factors are not included is not able to describe the intensity anomalies in these bands. As shown by Aliev et al.4, it is necessary to include these interactions into theoretical line strengths expressions. These authors have developed a third-order theory of the line strengths of the vibrational transition from the ground vibrational state to the rovibrational levels of molecules with C3v symmetry using the method of contact transformation applied to the electric dipole moment operator. A suitable expression for the line strength was derived to fit the experimental intensities. © 2010 American Institute of Physics.


Boussetta Z.,Laboratoire Of Physique Moleculaire | Aroui H.,Laboratoire Of Physique Moleculaire | Jacquemart D.,University Pierre and Marie Curie | Jacquemart D.,French National Center for Scientific Research | And 4 more authors.
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2011

The N2-broadening coefficients of CH3 79Br and CH3 81Br have been calculated for transitions belonging to the PP-, PQ-, PR-, RP-, RQ- and RR-branches of the v6 band near 10γm, using a semiclassical impact theory. The intermolecular potential used, includes in addition to the overwhelming electrostatic interactions, induction and dispersion energy contributions, which are significant only for low J transitions with K approaching or equal to J. Comparisons have been performed with the extensive set of previous measurements at room temperature [4]. The theoretical results are in satisfactory agreement with the experimental data, and the J and K dependences are reasonably well reproduced. From calculations at 200, 230, 260 and 296K, the temperature exponent of the collisional broadenings derived from a simple power law has been determined for each transition of each sub-branch and compared with a recent experimental evaluation [5]. Finally the N2-broadening coefficients calculated at 296K and their temperature exponents are given as supplementary materials of this paper for atmospheric applications and databases. © 2010 Elsevier Ltd.


Ben Mabrouk K.,Laboratoire Of Physique Moleculaire | Galalou S.,Laboratoire Of Physique Moleculaire | Aroui H.,Laboratoire Of Physique Moleculaire | Orphal J.,University Paris Diderot | Orphal J.,Karlsruhe Institute of Technology
Molecular Physics | Year: 2010

The present analysis improves previous measurements of self-broadening, self-shifting and self mixing of infrared ammonia in the wavenumber range 1000-1800 cm-1 at room temperature, based on spectra recorded using a high-resolution Fourier transform spectrometer Bruker IFS 120 HR. Previous studies in this spectral region catalogued numerous line-broadening, -shifting and -mixing. In the present paper, the corresponding spectroscopic parameters are obtained for 115 new lines in both v4 and 2v2 bands. The accuracies of self-broadening coefficients are about 3%. The mean accuracies of line-shifting and line-mixing data are estimated to be about 20% and 14%, respectively. As shown in a previous paper, the first-order Rosenkranz absorption coefficient taking into account line-mixing effects is adequate to extract with sufficient accuracy pressure-broadening as well as line-mixing and -shift parameters of self-perturbed NH3. Comparison of the results obtained with previous measurements and present theoretical calculations are given. © 2010 Taylor & Francis.


Gomez L.,University Pierre and Marie Curie | Gomez L.,French National Center for Scientific Research | Jacquemart D.,University Pierre and Marie Curie | Jacquemart D.,French National Center for Scientific Research | And 3 more authors.
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2010

A semiclassical impact theory based upon the Anderson-Tsao-Curnutte formalism has been used to calculate the self-broadening coefficients in the PP-, PQ-, PR-, RP-, RQ- and RR-branches of the ν6 band of 12CH379Br and 12CH381Br near 10μm. Comparisons have then been performed with the extensive set of previous measurements [3] (Jacquemart et al., 2007). The intermolecular potential used, involving the overwhelming electrostatic contributions, leads to larger results than the experimental data for middle J values. By arbitrarily limiting the integration of the differential cross-section to an impact parameter equal to 29Å, quite satisfactory results have been obtained, and the J and K dependences are in reasonable agreement with those observed experimentally. The theoretical results are, on the whole, slightly larger for CH379Br than for CH381Br and for same J and K initial states of the transitions they depend on the sub-branch considered. These differences and dependencies were not observed in the previous measurements due to scatter in the experimental data. Finally, the theoretical results obtained for all sub-branches of 12CH379Br and 12CH381Br are given as supplementary materials of this paper. © 2010 Elsevier Ltd.

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