ABOUT THE CHEMICAL COMPOSITION OF CARRIERS OF THE UNIDENTIFIED INFRARED BANDS (UIBs) AND PROTOPLANETARY EMISSION SPECTRA RECORDED FROM CERTAIN ASTRONOMICAL OBJECTS

摘要

In this communication we present the basic concept that the pure PAHs (Polycyclic Aromatic Hydrocarbons) can be considered only the ideal carriers of the UIBs (Unidentified Infrared Bands), the emission spectra coming from a large variety of astronomical objects. Instead we propose that the carriers of UIBs and of proto-planetary nebulae (PPNe) emission spectra are much more complex molecular mixtures possessing also complex chemical structures comparable to certain petroleum fractions. The demonstration of our proposal is based on the comparison between the emission spectra recorded from the protoplanetary nebulae (PPNe) IRAS 22272 + 5435 and the infrared absorption spectra of certain "heavy" petroleum fractions. It is shown that the best match with the reference spectrum is achieved with highly aromatic petroleum fractions having also partial kerogenic nature. Furthermore, it is introduced the concept of "statistical structural analysis" and "average statistical molecule" to describe extremely complex organic mixtures like those composing petroleum fraction, coal and coal fraction and hence also the protoplanetary nebulae. It is also shown that chemically modified petroleum fractions are able to match the infrared spectrum of anthracite, an high rank type of coal which has been proposed as the material responsible for the emission of the UIBs. It is shown that the petroleum fractions studied in this work, can be considered good candidates as carriers of the UIBs and hence as a reasonable alternative to coal as model of the matter present in the protoplanetary nebulae.