Emission Mechanism of Carbonaceous Interstellar and Circumstellar Dusts

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We have shown in a previous paper that oxidized f-QCC (Filmy Quenched Carbonaceous Composite) has absorption features that correspond to that of the interstellar 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3mum mnission features. Here we present new laboratory data showing that oxidized f-QCC, after heating to 500^ﾟC, has a 3.29 mum absorption feature that matches precisely the wavelength of the 3.29mum interstellar emission feature. In addition, the width of the fーQCC feature is close to that of the 3.29mum emission feature observed in NGC 7027, Orion, and IRAS 21282+5050. Laboratory spectra of polycyclic hydrocarbons (PAHs) were also obtained, and comparison of the fーQCC and PAH absorption opectra to that of the 3.29mum emission feature indicates the fーQCC provides much better match. We therefore suggest that fーQCC is representative of the class of material giving rise to the emission features in the interstellar medium.A red excess emission were observed in 12 objects among 24 reflection nebula by Witt and Boroson (1990). The emission spectra were single broad features peaked at 650-700nm with about 130nm of FWHM. Witt and Boroson attributed them to the fluorescence of hydrogenated amorphous carbon dusts. We collected QCCs on a substrate at a temperature lower than room temperature. The QCCs were mixture of low molecular weight chemical species such as molecules and radicals. They emit fluorescence under UV irradiation. The spectra of fluorescence of QCCs agreed well to the observed red excess emissions.In order to analyze an IR spectrum of interstellar and circumstellar dust, it is necessary to measure an emission spectrum of a candidate dust material. We examined a simple method for IR emission measurement using a sample compartment emission accessory, made by Connecticut Instrument U.S.A. We achieved a test measurement with the accessory, and obtained a preliminary result.