Radiofrequency spectra of ethyl fluoride recorded with two-dimensional Fourier transform spectroscopy using a coaxial sample cell

Abstract We describe a new experimental method in two-dimensional radiofrequency-microwave spectroscopy by using a coaxial sample cell. This technique allows to determine simultaneously transition frequencies in the RF range from about 1–600 MHz as well as in the MW range from about 1–4 GHz and was applied to investigations on ethyl fluoride in the ground state of the methyl torsion. The results show an interesting feature of Q-branch a -type lines in the RF range which is due to linear angular momentum terms in the effective Hamiltonian for the torsional E-states. The experimental frequencies are in good agreement with the applied theory.