Determination of nuclear spin-rotation coupling constants in CF3I by chirped-pulse Fourier-transform microwave spectroscopy

The rotational spectrum of CF3I in the ground vibrational state has been re-measured using a chirped-pulse Fourier-transform microwave spectrometer recently constructed at the University of Bristol. The new spectrometer provides the capability to acquire broadband rotational spectra throughout an operational frequency range of 7-18 GHz. The frequencies of ninety-nine F1′-F1″ transitions in three distinct JK′-JK″ bands have been recorded during an experiment which required only a couple of hours of data collection. Many of these transitions have additionally been re-measured using a Balle-Flygare, Fourier-transform microwave spectrometer. Fitting the data to the Hamiltonian for a C3v prolate, symmetric top has allowed the determination of new spectroscopic parameters. The rotational constant, B0, and nuclear quadrupole coupling constant, χaa(I), are consistent with the results provided in earlier works. The nuclear magnetic spin-rotation constants, Cperp.(I) and Cperp.(F), have been independently determined for the first time. These parameters are evaluated as 6.92(5) kHz and 2.37(11) kHz respectively. A technical description of the new CP-FTMW instrument is presented.