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3 Results

We show the spectral sequence of the thermally annealed QCC in the 3 $\mu $m region in Fig. 1. The emission and absorption spectra are collected in the left and the middle panels respectively. The spectra are arranged in order of the annealing temperature from the top to the bottom. In the right panel, we display spectra of PPNe with various spectroscopic characters for comparison.


  \begin{figure}\par\resizebox{8.8cm}{!}{\includegraphics{ds9205f2.ps}}\end{figure} Figure 2: The emission spectrum of an as-deposited QCC sample decomposed into five Gaussian components. The band centered at 3.30 $\mu $m is assigned to the aromatic sp2 CH stretching mode blended with the olefinic sp2 CH2. The bands at 3.38, 3.42, 3.48 $\mu $m are due to symmetric and antisymmetric stretching C-H vibrations in sp3 CH2 and CH3 chemical groups. The assignment of the 3.53 $\mu $m band is somewhat uncertain. The sum of the Gaussian components is shown in dot-dashed line

In Fig. 2 we decompose the emission spectrum of as-deposited film into five Gaussian components of various C-H vibrational modes according to the band assignment in the literatures on amorphous carbon (Dischler et al. [1983]; Bounouh et al. [1995]). The band centered at 3.30 $\mu $m is assigned to the aromatic sp2 CH stretching mode blended with the olefinic sp2CH2. The bands at 3.38, 3.42, 3.48 $\mu $m are due to symmetric and antisymmetric stretching C-H vibrations in sp3 CH2 and CH3chemical groups. The assignment of the 3.53 $\mu $m band is somewhat uncertain.


  \begin{figure}\par\resizebox{8.8cm}{!}{\includegraphics{ds9205f3.ps}}\end{figure} Figure 3: The over all emission spectra of QCC samples including continuum emission

In Fig. 3 we present the overall thermal emission of QCC samples before and after the thermal annealing at 740 K. The CaF2substrates used in the measurement have very low emissivity and no spectral features in the wavelength region, and furthermore we cancel out the minor contribution due to the substrate by subtracting its spectrogram from that of the QCC sample. Thus we consider the emissions observed here are certainly originated from QCC material itself. The absolute intensity of the QCC emission is calibrated by blackbody radiation of room temperature measured in the same configuration. Note that the QCC sample before and after the annealing is not equal in quantity. The emission features at $3.3-3.6~\mu$m are by far strong in the as-deposited QCC.


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