The CF Radical: Terahertz Spectrum and Detectability in Space

Abstract

Pure rotational transitions of the CF radical in its X2Π3/2,1/2 states have been observed with two terahertz spectrometers using backward wave oscillators as radiation sources. The radical was generated by a DC discharge in a gaseous mixture of CF4 and Ar. We have measured 48 rotational lines in the frequency range from 455 to 1072 GHz covering J-values as high as 12.5. The achieved frequency precision is about 50 kHz, which is comparable to that of conventional microwave spectroscopy. In addition to these pure rotational transitions, two direct transitions between the 2Π3/2 and 2Π1/2 states near 1062 GHz (J = 20.5-21.5) have been identified for the first time. Together with the zero-field rotational transition frequencies available in the literature, the present data were analyzed by a least-squares fitting procedure using an effective Hamiltonian for the 2Π states. The determined constants are complete and accurate enough to predict new line positions with low estimated uncertainties of less than ~170 kHz in the sense of a 3 σ deviation. These predictions should assist future astronomical searches of CF in the millimeter- and submillimeter-wave region.