The anion was identified in astronomical observations of the dark cloud TMC-1 and in the envelope of the late-type star CW Leonis by
(1) J. Cernicharo, J. R. Pardo, C. Cabezas, M. Agúndez, B. Tercero, N. Marcelino, R. Fuentetaja, M. Guélin, and P. de Vicente, 2023, Astron. Astrophys. 670, Art. No. L19.
We employed uncertainties essentially equal to those implicitely employed in (1), a factor of two smaller than reported. We used all lines toward CW Leonis, except the J = 27 – 26 line because of a large residual. calculations above 90 GHz should be viewed with caution.
The dipole moment was taken from a quantum-chemical calculation by
(2) P. Botschwina and R. Oswald, 2008, J. Chem. Phys. 129, Art. No. 044305.