The diffuse interstellar bands are absorption lines seen towards reddened stars1. None of the molecules responsible for these bands have been conclusively identified2. Two bands at 9,632 ångströms and 9,577 ångströms were reported in 1994, and were suggested to arise from C60+ molecules (ref. 3), on the basis of the proximity of these wavelengths to the absorption bands of C60+ measured in a neon matrix4. Confirmation of this assignment requires the gas-phase spectrum of C60+. Here we report laboratory spectroscopy of C60+ in the gas phase, cooled to 5.8 kelvin. The absorption spectrum has maxima at 9,632.7 ± 0.1 ångströms and 9,577.5 ± 0.1 ångströms, and the full widths at half-maximum of these bands are 2.2 ± 0.2 ångströms and 2.5 ± 0.2 ångströms, respectively. We conclude that we have positively identified the diffuse interstellar bands at 9,632 ångströms and 9,577 ångströms as arising from C60+ in the interstellar medium.
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This work was financially supported by the European Research Council (ERC-AdG-ElecSpecIons: 246998)
The authors declare no competing financial interests.
Extended data figures and tables
Gas-phase spectrum recorded by monitoring the depletion on the C60+–He mass channel using 1.5 mW (black) and 14 mW (red). Gaussian fits to experimental data (circles) are represented by solid lines, and give FWHMs of 2.5 ± 0.2 Å and 4.1 ± 0.2 Å at 1.5 mW and 14 mW, respectively. The blue dashed line shows a Gaussian with a FWHM of 2.5 Å.
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Campbell, E., Holz, M., Gerlich, D. et al. Laboratory confirmation of C60+ as the carrier of two diffuse interstellar bands. Nature 523, 322–323 (2015). https://doi.org/10.1038/nature14566
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