B. H. Foing and P. Ehrenfreund,
reported on the
Detection of two Interstellar Absorption Bands Coincident with Spectral Features of C₆₀⁺
Nature 369, 296 (1994).
Two weak diffuse interstellar bands at 963.2 and 957.7 nm were detected in absoption toward several reddened stars. The were assigned to C₆₀⁺ on the basis of laboratory electronic spectra of the molecular catio isolated in neon matrix. These features were blue-shifted less than 0.1 % from the strongest matrix bands. Even though the level of agreement is in the normal range, the identification was not beyond doubt.

J. Fulara, M. Jakobi, and J. P. Maier,
reported on
Electronic and Infrared Spectra of C₆₀⁺ and C₆₀^– in Neon and Argon Matrices
Chem. Phys. Lett. 211, 227 (1993).

Very recently, E. K. Campbell, M. Holz, D. Gerlich, and J. P. Maier,
reported on the
Laboratory Confirmation of C₆₀⁺ as the Carrier of Two Diffuse Interstellar Bands
Nature 523, 322 (2015).
The authors determined gas phase wavelengths of two strong electronic absorption features of C₆₀⁺ (957.75 and 963.27 nm), but also for two weaker ones (942.85 and 936.59 nm).

Finally, G. A. H. Walker, D. A. Bohlender, J. P. Maier, and E. K. Campbell,
reported on the
Identification of More Interstellar C₆₀⁺ Bands
Astrophys. J. 812, Art. No. L8 (2015).
In fact, the authors detected the two weaker features toward the stars HD 183143 and HD 169454, the latter from archival data. This detection dispels any possibly remaining doubt on the detection of this molecular cation.

Meanwhile, S. Iglesias-Groth and M. Esposito,
reported on the
A Search for near Infrared Bands of the Fullerene Cation C₆₀⁺ in the Protoplanetary Nebula IRAS 01005+7910
Astrophys. J. 776, Art. No. L2 (2013).
The authors detected the two stronger features in absorption.

Before, O. Berné, G. Mulas, and C. Joblin,
reported on
Interstellar C₆₀⁺
Astron. Astrophys. 550, Art. No. L4 (2013).
Severeal weak infrared emission features detected in a specific position of the reflection nebula NGC 7023 were assigned to stronger bands of C₆₀⁺ based on comparsion with matrix IR spectra.

Contributor(s): H. S. P. Müller; 10, 2015