First Astronomical Detection of the CF+ Ion

We report the first astronomical detection of the CF$^+$ (fluoromethylidynium) ion, obtained by recent observations of its $J = 1-0$ (102.6 GHz), $J = 2-1$ (205.2 GHz), and $J = 3-2$ (307.7 GHz) pure rotational emissions toward the Orion Bar. Our search for CF$^+$ — carried out using the IRAM 30m and APEX 12m telescopes—was motivated by recent theoretical models that predict CF$^+$ abundances of a $\rm few \times 10^{-10}$ in UV-irradiated molecular regions where C$^+$ is present. The measurements confirm the predictions. They provide support for our current theories of interstellar fluorine chemistry, which suggest that hydrogen fluoride should be ubiquitous in interstellar gas clouds.