Search results for "Vibrational polyads"
showing 4 items of 4 documents
Global modeling of the lower three polyads of PH_{3} Preliminary results
2009
International audience; In order to model the high-resolution infrared spectrum of the phosphine molecule in the 3 mu m region, a global approach involving the lower three polyads of the molecule (Dyad, Pentad and Octad) as been applied using an effective hamiltonian in the form of irreducible tensors. This model allowed to describe all the 15 vibrational states involved and to consider explicitly all relevant ro-vibrational interactions that cannot be accounted for by conventional perturbation approaches. 2245 levels (up to J=14) observed through transitions arising from 34 cold and hot bands including all available existing data as well as new experimental data have been fitted simultaneo…
Collisional Broadening, Line Shifting, and Line Mixing in the Stimulated Raman 2-v2 Q-Branch of CH4
1991
0021-9606; Self-, argon-, and helium-broadening coefficients have been measured for 13 lines in the 2v2 Raman Q branch of CH4 using stimulated inverse Raman spectroscopy. The linewidths clearly show the symmetry-state dependence characteristic of pressure broadening, and inelastic processes in general, involving spherical-top molecules. Pressure-induced line shifts have also been measured for these features in pure methane. The pressure-shift coefficients do not display the symmetry-state dependence found for the linewidths. By applying the Rosenkranz perturbation treatment to a pair of collisionally mixed lines, we have been able to obtain an estimate of individual state-to-state contribut…
Preliminary-Analysis of the Pentad of 13CH4 from Raman and Infrared-Spectra
1991
0022-2852
Spherical Top Theory and Molecular Spectra
2011
In this article, we present an overview of the present state of the art of the theory of high-resolution spherical-top spectra in the framework of the effective Hamiltonian approach. We describe the specific features of this class of molecules to explain the basic concepts of the theoretical methods used for the analysis (line positions and intensities) and the simulation of absorption (including pure rotation) and Raman spectra of such species. The non conventional formalism that we use is essentially based on irreducible tensor methods and is especially adapted to computational treatments and global analyses of complex interacting band systems. We give examples concerning mainly methane (…