Cyclic C${}_4^{+}$ as the carrier of the diffuse interstellar band at 503.9 nm?

Abstract

The diffuse interstellar bands (DIBs) have remained a mystery in astronomy since their discovery over a century ago. The only currently known carrier is C${}_{60}^{+}$ responsible for five DIBs, while more than 550 are yet to be interpreted. The spectra of short carbon chain cations C${}_n^{+}$, which are considered one of the most promising classes of species for the role of carriers of DIBs, are successfully recorded using He-tagging spectroscopy. The comparison of laboratory spectra with the observations demonstrates a close match of two absorption bands of C${}_4^{+}$ with the broad DIB at 503.9 nm. This defines a high abundance of these ions in the interstellar medium (ISM), which should exceed those of other similar-sized carbon chain cations. It is anticipated that all other short carbon chain cations will exhibit linear geometry and, as a consequence, will have a long vibrational progression. However, the distinctive cyclic geometry of C${}_4^{+}$ is postulated to underpin the elevated abundance of these ions in the ISM, as well as the distinctive spectrum of this ion, which displays a single strong, relatively narrow absorption band that exceeds in intensity all other absorption bands in the visible range.

References in corpus (3)

• Confirming interstellar C${}_{60}^{+}$ using the Hubble Space Telescope
• Highly charged droplets of superfluid helium
• The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment