All Figures

$\begin{figure} \par\includegraphics[height=22.2cm,width=8.7cm,clip]{h4223f01.eps... ...{6mm} \includegraphics[height=22.2cm,width=8.7cm,clip]{h4223f02.eps}\end{figure}$ Figure 1: ISO spectra are plotted in region of 2-25 $\mu$ m for the 9 carbon stars (left panel) in group A and the 11 carbon stars (right panel) in group B. Different emission and absorption features are identified and marked by vertical lines and related letters. Marks in the figures are: "a'' represents C₂H₂+CO; "b'', HCN+ C₂; "c'', HCN+ C₂H₂,; "d'', C₃; "e'', SiC and "f'', C₂H₂. Labels (such as "00172+4425'') above spectra are the IRAS name of the objects; labels (such as "( $\times$ 1,+100)'' below spectra mean that spectra are first multiplied by a factor (such as " $\times$ 1'') and then shifted by adding an amount (such as "+100'').
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In the text

$\begin{figure} \par\includegraphics[height=22.4cm,width=8.7cm,clip]{h4223f03.eps... ...6mm} \includegraphics[height=22.4cm,width=8.7cm,clip]{h4223f04.eps} \end{figure}$ Figure 2: ISO spectra are plotted for the region of 2-45 $\mu$ m for the 4 carbon stars (left panel) in group C and the 5 carbon stars (right panel) in group D. Different emission and absorption features are identified and marked by vertical lines and letters. The marks and labels in this figure are the same as in Fig. 1.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f05.eps} \end{figure}$ Figure 3: Diagram of the normalized spectral profiles for the two unidentified absorption features (the 3.50 and 3.65 $\mu$ m features) found in the five objects of group A.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f06.eps} \end{figure}$ Figure 4: Normalized spectral profiles of the 3.05 $\mu$ m C₂H₂+HCN absorption feature for 25 objects. They are grouped in three panelsaccording to our classification for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f07.eps} \end{figure}$ Figure 5: Diagram of the relative integrated flux against $T_{\rm nir}$ for the 3 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f08.eps} \end{figure}$ Figure 6: Diagram of the relative integrated flux against the normalized line center depth for the 3 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f09.eps} \end{figure}$ Figure 7: Diagram of the relative integrated flux against the normalized line center depth for the 5 $\mu$ m C₃ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f10.eps} \end{figure}$ Figure 8: Diagram of the relative integrated flux against $T_{\rm nir}$ for the 5 $\mu$ m C₃ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f11.eps} \end{figure}$ Figure 9: Diagram of the relative integrated flux ratio of the 3.05 and 5.20 $\mu$ m feature against $T_{\rm nir}$ . Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4223f12.eps} \end{figure}$ Figure 10: Diagram of the peak wavelength against the relative integrated flux for the 11 $\mu$ m SiC feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f13.eps} \end{figure}$ Figure 11: Diagram of the relative integrated flux against the normalized line peak height for the 11 $\mu$ m SiC feature. Different lines are derived by fitting data of different groups respectively. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f14.eps} \end{figure}$ Figure 12: Diagram of the relative integrated flux of 11 $\mu$ m SiC feature against that of the 3.05 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4223f15.eps}\end{figure}$ Figure 13: Diagram of the relative integrated flux of 11 $\mu$ m SiC feature against that of the 13.70 $\mu$ m C₂H₂ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f16.eps}\end{figure}$ Figure 14: Comparison of the typical 13.70 $\mu$ m C₂H₂ absorption profiles from the four groups. The dashed line is for group-A object IRAS 03374+0106; the dotted line for group-B object IRAS 17556+5813; the dash-dot-dot line for group-C object IRAS 03229+4721; the short-dotted line for group-D object IRAS 02293+5342.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f17.eps} \end{figure}$ Figure 15: Diagram of the relative integrated flux against the normalized line center depth for the 13.70 $\mu$ m C₂H₂ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle. The different lines are derived by linearly fitting the points of groups A and D respectively. One object in group D, IRAS 21027+5309, has been excluded when fitting group D, because it is far away from the other four sources in group D.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f18.eps} \end{figure}$ Figure 16: Diagram of the relative integrated flux of the 13 $\mu$ m C₂H₂ feature against that of the 3.05 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square. The dashed line is derived by linearly fitting the points of group A.
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In the text

$\begin{figure} \par\includegraphics[height=22.4cm,width=8.7cm,clip]{h4223f03.eps... ...6mm} \includegraphics[height=22.4cm,width=8.7cm,clip]{h4223f04.eps} \end{figure}$	Figure 2: ISO spectra are plotted for the region of 2-45 $\mu$ m for the 4 carbon stars (left panel) in group C and the 5 carbon stars (right panel) in group D. Different emission and absorption features are identified and marked by vertical lines and letters. The marks and labels in this figure are the same as in Fig. 1.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f05.eps} \end{figure}$	Figure 3: Diagram of the normalized spectral profiles for the two unidentified absorption features (the 3.50 and 3.65 $\mu$ m features) found in the five objects of group A.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f06.eps} \end{figure}$	Figure 4: Normalized spectral profiles of the 3.05 $\mu$ m C₂H₂+HCN absorption feature for 25 objects. They are grouped in three panelsaccording to our classification for comparison.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f07.eps} \end{figure}$	Figure 5: Diagram of the relative integrated flux against $T_{\rm nir}$ for the 3 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f08.eps} \end{figure}$	Figure 6: Diagram of the relative integrated flux against the normalized line center depth for the 3 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f09.eps} \end{figure}$	Figure 7: Diagram of the relative integrated flux against the normalized line center depth for the 5 $\mu$ m C₃ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f10.eps} \end{figure}$	Figure 8: Diagram of the relative integrated flux against $T_{\rm nir}$ for the 5 $\mu$ m C₃ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f11.eps} \end{figure}$	Figure 9: Diagram of the relative integrated flux ratio of the 3.05 and 5.20 $\mu$ m feature against $T_{\rm nir}$ . Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4223f12.eps} \end{figure}$	Figure 10: Diagram of the peak wavelength against the relative integrated flux for the 11 $\mu$ m SiC feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f13.eps} \end{figure}$	Figure 11: Diagram of the relative integrated flux against the normalized line peak height for the 11 $\mu$ m SiC feature. Different lines are derived by fitting data of different groups respectively. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f14.eps} \end{figure}$	Figure 12: Diagram of the relative integrated flux of 11 $\mu$ m SiC feature against that of the 3.05 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{h4223f15.eps}\end{figure}$	Figure 13: Diagram of the relative integrated flux of 11 $\mu$ m SiC feature against that of the 13.70 $\mu$ m C₂H₂ feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square; group-D sources by a triangle.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f16.eps}\end{figure}$	Figure 14: Comparison of the typical 13.70 $\mu$ m C₂H₂ absorption profiles from the four groups. The dashed line is for group-A object IRAS 03374+0106; the dotted line for group-B object IRAS 17556+5813; the dash-dot-dot line for group-C object IRAS 03229+4721; the short-dotted line for group-D object IRAS 02293+5342.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{h4223f18.eps} \end{figure}$	Figure 16: Diagram of the relative integrated flux of the 13 $\mu$ m C₂H₂ feature against that of the 3.05 $\mu$ m C₂H₂+HCN feature. Group-A sources are represented by a cross; group-B sources by a circle; group-C sources by a square. The dashed line is derived by linearly fitting the points of group A.
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