Analysis of torsional spectra of molecules with two internal C3v rotors. XXIV. High resolution far infrared spectra of acetone‐d0, ‐d3, and ‐d6

The high resolution (0.10 cm−1) far infrared spectra of gaseous acetone‐d0, ‐d3, and ‐d6 were measured between 370 and 40 cm−1. The region of the methyl torsional transitions below 130 cm−1 was analyzed in terms of the semirigid rotor model for molecules with two internal C3v rotors and the two‐dimensional torsional potential functions were determined. Effective barriers of 291 cm−1 (832 cal/mol) and sine–sine interaction terms of −l08 cm−1 (−309 cal/mol) were found for all three isotopic species. The results are compared with those from ab initio calculations and from the analysis of splittings in the microwave spectrum.

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