SYNTHESIS OF THE SI-C FINE GRAINS HAVING 11 MICRONS BROAD FEATURE.

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In our galaxy 10 <micrn> m broad spectra of the circumstellar dust are observed in circumstellar envelopes of o-rich stars and 11<micrn> m broad spectra are observed in envelopes of C-rich stars. These 11 <micrn> m emission are thought to be caused by si-c dusts. It is difficult to form directly Si-C dusts from Si-C molecules or radicals artificially. We assumed that the Si-C dusts are formed form a mixture of SiO and C-containing molecules and radicals. We try to form Si-C dusts as follows; in first step we form rapidly cooled condensates form SiO molecular beam and in second step we form Si-C grains from a mixture of the SiO condensates and the C-containing molecules and radicals. SiO molecular beam was ejected from the mixture of SiO_2 + Si in Ta boat by electrical heating at 1,300 ゜c. SiO gas was detected with quadrupole massspectrometer. Rapidly cooled SiO condensates were obtained and analyzed with X ray diffractometer and electron spin resonance (ESR) apparatus. X ray analysis showed that they have glassy structre of Si-O and ESR measurement shows that they have unpaired electrons. They were highly active chemically. They were classified to two types; One was a condensate from SiO molecule gas called "Molecule Frost" and the other condensate was formed from dense SiO gas called "Cluster Frost". When Molecule Frost and Cluster Frost were heated to 400 ゜c , change of their structure were found with IR spectra measurements. They reacted with H_2O easily at -200 ゜c. Using the SiO condensates we will produce Si-C dusts in nect step.