MILLIMETER AND SUBMILLIMETER REST FREQUENCIES FOR THE MGF RADICAL

The pure rotational spectrum of the MgF radical in its ground X 2SIGMA+ electronic state has been observed in the laboratory using millimeter/submillimeter direct absorption spectroscopy. Rotational transitions arising from the upsilon = 0, 1, 2, and 3 vibrational modes of the main magnesium isotopic species, (MgF)-Mg-24, have been recorded, as well as those arising from the upsilon = 0 state of the Mg-25 and Mg-26 isotopomers. Rotational and fine-structure constants have been determined for these molecules, as well as hyperfine parameters for both the F-19 (I = 1/2) and Mg-25 (I = 5/2) nuclei. The rest frequencies presented here for MgF have an estimated accuracy of +/- 200 kHz, and will enable astronomical searches to be carried out for this fluoride radical. Magnesium fluoride may be present in the late-type carbon star IRC + 10216, where AlF appears to be abundant.