Rotational and Torsional Properties of Various Monosubstituted Isotopologues of Acetone (CH3-CO-CH3) from Explicitly Correlated Ab Initio Methods

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Geometric and spectroscopic parameters are determined using explicitly correlated coupled cluster ab initio calculations (CCSD(T)-F12) for five monosubstituted isotopologues of acetone containing 18O, 13C, and D. The far-infrared region is explored with a variational procedure of reduced dimensionality that takes the interconversion of the nine minima of the potential energy surface into consideration. The methyl torsional barrier of the main isotopologue, computed to be 245.7 cm-1, varies slightly with the isotopic substitution. In the monodeuterated species, the two inequivalent internal rotors are hindered by two inequivalent barriers of 244.0 and 244.7 cm-1. The torsional fundamentals of the main variety are localized at 78.636 cm-1 (ν12) and 128.904 cm-1 (ν17). The differences between splitting components are lower than 0.02 and 0.2 cm-1 in the main isotopologue and in the isotopologues containing 18O and 13C, respectively. In the monodeuterated species the subcomponents are separated by ∼15 cm-1.
This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant Agreement No. 872081. This research was supported by the Ministerio de Ciencia, Innovación y Universidades of Spain through the Grants EIN2019-103072 and FIS2016-76418-P. This work has received funding from the CSIC i-coop+2018 Program under the Reference Number COOPB20364. The authors acknowledge the CTI (CSIC), CESGA, and the “Red Española de Computación” for Grants AECT-2020-2-0008 and RES-AECT2020-3-0011 for the computing facilities.