6533b86dfe1ef96bd12c97d3

RESEARCH PRODUCT

Spherical Top Theory and Molecular Spectra

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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 (CH4) and sulfur hexafluoride (SF6). The efficiency of these methods is not restricted to spherical tops, as they also apply to other molecular species or spectroscopic problems. We demonstrate this through recent developments including the modeling of the effects of collisions on line shapes, the modeling of rovibronic effects, as well as extensions to molecules with lower symmetry. The computer implementation of the methods is an integral part of the modeling. We conclude the article with an overview of the free access programs and databases developed in the Dijon group for spherical-top molecules and some other species. Keywords: spherical tops; rovibrational spectroscopy; group theory; tensorial formalism; vibrational polyads; methane; sulfur hexafluoride; collisional broadening; extension to lower symmetries; rovibronic spectra; programs and databases