THE FAR-INFRARED SPECTRUM OF METHYL-CHLORIDE - DETERMINATION AND ORDER OF MAGNITUDE OF THE SEXTIC CENTRIFUGAL-DISTORTION CONSTANTS IN SYMMETRICAL TOPS

The submillimeter-wave spectra of the ground state rotational transiti ons of (CH3Cl)-Cl-35 and (CH3Cl)-Cl-37 were measured up to 1.9 THz. Th e far-infrared spectrum of (CH3Cl)-Cl-35 was also Measured in the regi on 35-50 cm-1 using an interferometric spectrometer (Bruker IFS 120 HR ). Rotational and centrifugal distortion (up to sixth order) constants were determined for both isotopic species. The accuracy of the sextic centrifugal distortion constants is discussed. It is shown that it is possible to predict the sign and order of magnitude of the sextic con stants of a symmetric-top molecule. (C) 1994 AcademiC Press, Inc.