Analysis of carbonaceous materials which show "217.5<plus-minus>2.5 nm hum

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Interstellar extinction curve is a spectrum of interstellar dust in our Galaxy. In the spectrum we can see a clear 217.5 nm hump and and very broad-500 nm hump.QCC (Quenched Carbonaceous Composite) is an amorphous carbonaceous material formed from a hydrocarbon plasma. In a previous paper (Sakata et al.1994), we have studied two forms of QCC : a dark QCC component located near the plasmic beam and a thermally-altered filmy QCC.Both types of QCC derivatives show an absorption feature near 217 nm but with different extinction magnitude. And we showed that soots produced from methane, methane-hydrogen gas mixtures, have a broad extinction feature centered at about 217 nm.In this work we present a new material, mesophase pitch, which has a 217 nm extinction feature. The mesophase pitch was produced from raw pitch by heating to -450 C,by Asahi Coke Ltd. Chemical analysis of the mesophase pithc showed H/C=0.52.These three kinds of materials showing about 217 nm hump were formed under hydrogen rich environment. From the chemical composition of mesophase pitch, we can deduce that the carbonaceous materials having 217 nm feature contain a large amount of hydrogen in their structure.