Structural and spectroscopic characterization of various isotopologues of 2-hydroxyacetonitrile using highly correlated ab initio methods

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Various isotopologues of 2-hydroxyacetonitrile (OHCHCN), a detectable astrophysical molecule, are characterized using explicitly correlated coupled cluster theory (CCSD(T)-F12/AVTZ-F12). Rovibrational parameters and far infrared transitions are computed to help the interpretation of the rotational spectra and radioastronomical observations. OHCHCN displays non-rigid properties. The OH internal rotation intertransforms two conformers, gauche and trans, whose energy separation reaches 1.41 kcal/mol. The process is restricted by energy barriers of V = ~ 645 cm and V = ~ 425 cm. Isotopic effects on the rotational constants and on the torsional energy levels are evaluated for isotopic varieties containing the most abundant cosmological isotopes (C, C, N and D). Effects are relevant for ODCHCN where the ground vibrational state splits in two components separated by 0.51 cm. This gap has been evaluated to be 3.20 cm for the main isotopologue. Graphical abstract: [Figure not available: see fulltext.].
This research was supported by the FIS2013-40626-P and FIS2016-76418-P projects of the MINECO, Spain. The authors also acknowledge the COST Actions 1401 and 1405. S.D. acknowledges MAEC-ACID (Spain) for the grant.