Heavy petroleum fractions as possible analogues of carriers of the unidentified infrared bands

Abstract

The Fourier-transform infrared spectra and the electronic spectra of a series of petroleum fractions of different composition and origins have been studied. Furthermore, these fractions have been modified through the Scholl reaction, a reaction that causes an increase in the aromatic content of the fractions by causing the formation of polycyclic aromatic hydrocarbons (PAHs) or larger PAHs if they were already present in the pristine samples. It is shown that some heavily aromatic petroleum fractions are able to match the emission spectra of the protoplanetary nebula IRAS 22272+5435. Additionally, it is shown that the modified petroleum fractions are able to match the infrared spectrum of anthracite, a high-rank type of coal that has been proposed as the material responsible for the emission of the unidentified infrared bands (UIBs), but which can also be thought of as a model of the kerogen found in meteorites or assumed to be present in cometary nuclei. It is shown that the petroleum fractions considered in this work can be considered even better candidates than coal as a model for the matter present in protoplanetary nebulae and the carrier of the UIBs.