High precision far-infrared spectroscopy of molecules and ions preparing for the future detection of interstellar species in the far-infrared region

Rotational transition frequencies of molecules and molecular ions were measured precisely with an accuracy of several tens of kHz by using far-infrared spectrometer in Toyama University. Measured species were H_2D^+, NH_3, N_2H^+, and H_2F^+. Obtained spectral data supports the far-infrared investigations in several international research projects of interstellar species(such as ALMA, SOFIA, Herschel). Our data of H_2F^+will play an important role in searching for this species in space.