Infrared spectral sequence of quenched carbonaceous composite subjected to thermal annealing

We investigate the spectroscopic alteration through thermal annealing on the quenched carbonaceous composite (QCC) produced from hydrocarbon plasma. The emission and absorption spectra of QCC samples annealed at various temperatures indicate that the proportion of aliphatic C-H bonds in QCC decreases relative to aromatic C-H bonds with increase of annealing temperature. By comparing the spectra of annealed QCC with observed emission spectra of proto-planetary nebulae, similarity between the spectral sequence obtained in the laboratory and that in the observational data is clearly noticed. On this basis, we discuss a simple evolutional scenario of carbon dust in circumstellar environment around cool evolved stars.