Rotational Spectrum of the Formyl Cation, HCO+, to 1.2 THz

A variety of high-quality spectroscopic studies have contributed to knowledge of the formyl cation, HCO⁺, and its rare isotopologues, but technical limitations have previously limited precise determinations of the far-infrared, or terahertz spectrum. This study extends the microwave, millimeter, and submillimeter spectroscopy of HCO⁺ into the terahertz range. The resulting measurements and predictions are of sufficient coverage to adequately address astrophysical questions about this species using the Herschel Space Observatory or the Atacama Large Millimeter Array.