A coincidence between a hydrocarbon plasma absorption spectrum and the<i>λ</i>5450 DIB

Abstract

<i>Aims. <i/>The aim of this work is to link the broad <i>λ<i/>5450 diffuse interstellar band (DIB) to a laboratory spectrum recorded through expanding acetylene plasma.<i>Methods. <i/>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.<i>Results. <i/>In the 543–547 nm region a broad band is measured with a band maximum at 545 nm and <i>FWHM<i/> of 1.03(0.1) nm coinciding with a well-known diffuse interstellar band at <i>λ<i/>5450 with an <i>FWHM<i/> of 0.953 nm.<i>Conclusions. <i/>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.