Knowledge Bank

We have confirmed the identity of the interstellar ""X-ogen"" line as the$ J = 0 {\rightarrow} 1$ transition of $HCO+$ by observing it in a laboratory dc glow discharge in a hydrogen-carbon monoxide mixture at liquid nitrogen temperature. Source modulation and computer controlled signal averaging were employed. The frequency is in excellent agreement with the best astrophysical determinations. We have also seen the spectra of the $Hl3CO+$and $HC18O+$ species using enriched carbon monoxide and have obtained the molecular structure from these data. Work on further isotopic forms is in progress as are efforts to obtain the pressure broadening linewidth of $HCO+$ due to $H2$ pressure.