Theoretical study of the microwave spectrum of isotopologues of OCS-(He)2

Li, Hui; Liu, Yongdong; Jäger, Wolfgang; Le Roy, Robert J.; Roy, Pierre-Nicholas
November 2010
Canadian Journal of Chemistry;Nov2010, Vol. 88 Issue 11, p1146
Academic Journal
The rovibrational energy levels (J = 0-3) and rotational spectra of seven isotopologues of the OCS-(He)2 complex have been determined by numerically exact basis set calculations. The interaction energy is represented as a sum of two-body terms consisting of the OCS-He potential, which Howson and Hutson (J. Chem. Phys.2001,115, 5059) obtained at the CCSD(T)/aug-cc-pVTZ level of theory, and the He-He potential that Jeziorska et al. (J. Chem. Phys.2007,127,124303) obtained with SAPT theory. Three-body effects and the quality of the potential are discussed. Comparison with experiment shows that microwave transitions can be predicted by this additive approach with an accuracy equal or better than 0.7% for all the observed spectral lines. A method for the three-dimensional representation of the helium density in the body-fixed frame is presented that highlights the highly delocalized nature of the helium subsystem. Utilisant des ensembles de base numériquement exacts, on a calculé les niveaux d'énergie rovibrationnels (J = 0-3) et les spectres rotationnels de sept isotopologues du complexe OCS-(He)2. L'énergie d'interaction est représentée par la somme de termes à deux corps formée du potentiel OCS-He que Howson et Hutson (J. Chem. Phys.2001,115, 5059)ont déterminé au niveau CCSD(T)/aug-cc-pVTZ de la théorie et du potentiel He-He que Jeziorska et al. (J. Chem. Phys.2007,127, 124303) ont déterminé à l'aide de la théorie des perturbations adaptée pour la symétrie (TPAS). On discute aussi des effets de trois corps et de la qualité du potentiel. Une comparaison des résultats des calculs avec des résultats expérimentaux montre que les transitions de microondes peuvent être mieux prédites par cette approche additive, avec une précision égale ou meilleure à 0,7 % pour toutes les raies spectrales observées. On présente une méthode de représentation tridimensionnelle de la densité de l'hélium dans un squelette à corps fixes qui est caractérisé par la nature hautement délocalisée du sous-système de l'hélium.


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