THz rotational spectrum of H2F+.

In view of recent tremendous advance in astronomical observations in the submillimeter to THz region brought by the Herschel space craft, laboratory high-resolution spectroscopic investigations in that frequency region into unstable molecules, in particular, light hydride ions, are urgently needed. As a part of such endeavor, rotational transitions of H(2)F(+) were observed in the THz-region by using a tunable far-infrared spectrometer. These newly detected lines together with the submillimeter-wave lines obtained previously and the combination differences derived from infrared vibration-rotation lines were subject to a least-squares analysis that yielded a set of molecular constants with much better accuracy.