A coincidence between a hydrocarbon plasma absorption spectrum and theλ5450 DIB

Abstract

Aims. The aim of this work is to link the broad λ5450 diffuse interstellar band (DIB) to a laboratory spectrum recorded through expanding acetylene plasma. Methods. Cavity ring-down direct absorption spectra and astronomical observations of HD 183143 with the HERMES spectrograph on the Mercator Telescope on La Palma and the McKellar spectrograph on the DAO 1.2 m Telescope are compared. Results. In the 543-547 nm region a broad band is measured with a band maximum at 545 nm and FWHM of 1.03(0.1) nm coinciding with a well-known diffuse interstellar band at λ5450 with an FWHM of 0.953 nm. Conclusions. A coincidence is found between the laboratory and the two independent observational studies obtained at higher spectral resolution. This result is important, as a match between a laboratory spectrum and a -potentially lifetime broadened -DIB is found. A series of additional experiments were performed in order to unambiguously identify the laboratory carrier of this band, but this was not successful. The laboratory results, however, restrict the carrier to a molecular transient, consisting of carbon and hydrogen.

On the electronic spectroscopy of closed-shell cations derived from resonance-stabilized radicals: Insights from theory and Franck-Condon analysis

“…Despite decades of study into carbon chains, these have failed to conclusively account for the astronomical features (Maier et al 2004). Nevertheless, two recent matches between laboratory spectra and DIBs have been reported for the short carbon chains H 2 CCC and HCCCCH + ; however, these coincidences are still being debated (Linnartz et al 2010;Maier et al 2011b;Oka & McCall 2011;Krełowski et al 2011Krełowski et al , 2010. Indeed, after further scrutiny, HCCCCH + is now regarded as an unlikely carrier of a DIB due to mismatches in the band profile and central wavelength ).…”

Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions

“…In the past two decades the field has converged towards larger carbonaceous molecules, like the fullerenes and polycyclic aromatic hydrocarbons (PAHs), which have electronic transitions in the optical (see for example Salama et al 1999;Ruiterkamp et al 2005;Kokkin & Schmidt 2006;Zhou et al 2006;and Salama et al 2011). New diffuse bands have been detected in one line-of-sight which appear to match with naphthalene and anthracene cations (Iglesias-Groth et al 2008 and the weak 5450 Å DIB is found to match with an absorption band arising from a hydrocarbon plasma created in the laboratory (Linnartz et al 2010). Linear-C 3 H 2 has been put forward as a carrier of the 5450 and 4881 Å DIBs Based on observations collected at the European Southern Observatory, Paranal, Chile .…”

The Diffuse Interstellar Bands: an Elderly Astro-Puzzle Rejuvenated

“…Results for calculated transitions or inferred vibronic progressions of large molecules are promising but await further study and confirmation from lab experiments. This is also the case for the good comparison between a hydrocarbon plasma band and the 5449 DIB (Linnartz et al 2010 ) has been challenged by others, revealing inconsistencies between the observations and laboratory data (Oka & McCall, (2011), Krelowski (this volume)).…”