Microwave spectra of the 13C isotopic species of methyl cyanide for the ground and v8 = 1, 2 vibrational levels in the frequency range 17–56 GHz

Abstract The microwave spectrum of 13 C substituted methyl cyanide CH 3 C 14 N was studied for the v 8 = 1, 2, for both single and double 13 C substitutions, with vibrational states in the frequency range of 17 to 56 GHz. In addition, some rotational components for the ground state were remeasured and these results compared to those found in the literature for the naturally occurring isotopic ratios. The frequencies of the 1 ≤ J ≤ 3 components were measured for each vibration and these frequencies used to produce a constant set which can be used to predict overall frequencies of spectral components in the ground and v 8 = 1, 2 up to an accuracy of 100 KHz. Previously obtained experimental data, available from the literature for the naturally occurring isotopes, and our own data for the ground state are presented and compared with the frequencies obtained from a comprehensive equation derived from perturbation techniques.