Millimeter and submillimeter-wave spectroscopy of silicon difluoride

The rotational spectra of 28SiF2, 29SiF2, and 30SiF2 in their ground vibrational states, as well as those of 28SiF2 in the v1 = 1, v2 = 1, v3 = 1, and v2 = 2 excited states have been studied in selected frequency regions between 80 and 700 GHz. Transitions involving a large range of quantum numbers have been observed, so that precise rotational and quartic centrifugal distortion constants could be determined for each of the spectra investigated. In addition, the complete set of sextic distortion constants was also obtained for the most abundant isotopomer in its ground vibrational state. The quadratic and cubic force constants of silicon difluoride have been refined by a least-squares procedure using a larger and more precise set of data.