Fluoromethylidynium, CF⁺, may seem like an odd molecule. However, it is isoelectronic to CO with a similar rotational constant, but a dipole moment that is about ten times larger. Its detection toward the PDR Orion-Bar was reported by
D. A. Neufeld, P. Schilke, K. M. Menten, M. G. Wolfire, J. H. Black, F. Schuller, H. S. P. Müller, S. Thorwirth, R. Güsten, and S. Philipp,
Discovery of Interstellar CF⁺
Astron. Astrophys. 454, L37–L40 (2006).
The J = 1 – 0 and 2 – 1 transitions were detected with the IRAM 30 m telescope at 102.6 and 205.2 GHz, respectively, as well as the 3 – 2 transition with the APEX 12 m dish at 307.7 GHz.

The J = 1 – 0 transition was also detected in two 3 mm molecular line surveys carried out with the 20 m OSO telescope:
Spectral scan of the star-forming region DR21(OH). Observations and LTE analysis
Astron. Rep. 54, 295–316 (2010);
Spectral survey of the star-forming region W51 e1/e2 at 3 mm
Astron. Rep. 54, 1084–1104 (2010);
both by S. V. Kalenskii and by L. E. B. Johansson.
Details in the second article are more limited than in the first one. Because of the observation of only one line, the identifications were viewed somewhat tentatively. Nevertheless, the observation of HCO indicates PDR activity in the regions observed.

The more recent detection of the J = 1 – 0 and 2 – 1 transitions by
V. Guzmán, J. Pety, P. Gratier, J. R. Goicoechea, M. Gerin, E. Roueff, and D. Teyssier,
The IRAM-30m line survey of the Horsehead PDR\\ I. CF⁺ as a tracer of C⁺ and as a measure of the fluorine abundance
Astron. Astrophys. 543, Art. No. 1 (2012);
suggests that the cation is a fairly common PDR molecule. It is worthwhile mentioning that the line width in this source was particularly narrow that the 1 – 0 transition displayed ¹⁹F nuclear spin-rotation splitting.

H. S. Liszt, J. Pety, M. Gerin, and R. Lucas,
detected with the IRAM 30 m telescope
HCO, //c//-C₃H and CF⁺: three new molecules in diffuse, translucent and “spiral-arm” clouds
Astron. Astrophys. 564, Art. No. A64 (2014).

Contributor(s): H. S. P. Müller; 09, 2005; 08, 2006; 11, 2012; 05, 2015