Rotational spectrum of trifluoroidomethane

Abstract

The rotational spectra for the ground vibrational states of ¹²CF₃I and ¹³CF₃I have been re-examined with greater precision and at frequencies up to 204 GHz or J″= 66 and up to 115 GHz for J″= 37, respectively. The rotational spectra of the excited vibrational states ν₃= 1 and ν₆= 1 have been measured and assigned, with the help of radiofrequency–microwave double resonance, for the ¹²CF₃I species up to J″= 40 and 45, respectively; i.e. frequencies of 125 and 140 GHz. The states are distinguished from each other by the clear effects of the angular momentum of ν₆= 1 state, for which |l|= 1. Anomalous values of the centrifugal distortion terms are examined and shown to be due to a Coriolis resonance between these two states which are only ca. 20 cm^–1 apart. Full details of the rotational parameters are given in tables 1 and 2.