Millimeter-Wave Rotational Spectra of the37Cl Species of 1,1,1-Trichloroethane

Abstract

The mm-wave rotational spectrum of the three isotopic species which result from37Cl isotopic substitution in 1,1,1-trichloroethane was studied in the region 121–472 GHz, and for transitions withJ″ up to 100. The symmetry equivalence of the three chlorine nuclei makes the rotational spectrum of35Cl237ClCCH3comparable in intensity to that of the parent species, so that it accounts for a large proportion of the mm-wave spectral intensity. Accurate spectroscopic constants have been determined for all studied isotopic species, and evolution of their values relative to those of the parent species has been studied. The magnitudes of the constanth3in the asymmetric top37Cl1and37Cl2species are in excellent agreement with that for the symmetric top parent species and show that, under suitable conditions, the measurement of the asymmetric top species arising from isotopic substitution can provide a less demanding route for determination ofh3than in the parent symmetric top molecule.