[mscholz]

The Nature paper describes electronic spectroscopy of the ionized C60+, where light from the near-IR to the UV is used to excite electronic, rather than vibrational or rotational, transitions.

Indeed, this is how the presence of C60+ in the interstellar medium was absolutely confirmed (and was the first assignment of such a near-IR to UV absorption line from the interstellar medium).[0]

The problem with the Ehrenfreud paper is that the spectrum was recorded in frozen neon and the interaction between the analyte (C60+) and its matrix (frozen neon) is strong enough such that the perturbation is larger than the certainty of the positions of the spectral lines. Definitive laboratory assignments therefore require studying the molecules under (as close to) identical conditions as the interstellar environment, including high vacuum and low temperature.

The detection of neutral C60 was, as you say, performed using infrared (vibrational) spectroscopy.[1]

[0] https://www.nature.com/articles/nature14566

[1] https://science.sciencemag.org/content/329/5996/1180