$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1571fig1.eps} \end{figure}$	Figure 1: Main reactions for the formation of the $\rm C_2$ and $\rm C_3$ radical. The thickness of the arrow indicates the importance of the reaction. The dotted arrow denotes the hypothetical reaction for the electron impact dissociation of C₃H₄. Thick boxes mark molecules that have been observed.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig2.eps} \end{figure}$ Figure 2: Water production rate (diamonds) estimated for the model input and water production rates (crosses) measured by Weaver et al. (1999b) and (stars) Dello Russo et al. (2000).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig3.eps} \end{figure}$ Figure 3: Flowchart for obtaining abundance ratios using the ComChem model.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{1571fig4.eps} \end{figure}$ Figure 4: Overview of the best fitting $\rm C_3$ profiles (triangles - sunward, diamonds - tailward, negative heliocentric distances denote preperihelion observations).
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{1571fig5.eps} \end{figure}$ Figure 5: Overview of the best fitting $\rm C_2$ profiles (triangles - sunward, diamonds - tailward, negative heliocentric distances denote preperihelion observations).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig6.eps} \end{figure}$ Figure 6: Evolution of abundance ratios over heliocentric distance.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig7.eps} \end{figure}$ Figure 7: Evolution of abundance ratios relative to water and to carbon monoxide over heliocentric distance.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{1571fig8a.eps}\par\vspace*{2mm} \includegraphics[width=6.5cm,clip]{1571fig8b.eps} \end{figure}$ Figure 8: Upper panel: abundance ratio of C₂H₆ relative to C₂H₂ versus heliocentric distance. The solid line is the mean value derived in this work, the dotted lines show the associated error. The values determined by Dello Russo et al. (2001) are displayed for comparison. Lower panel: evolution of the abundance ratios of C₃H₄ to C₂H₂ and C₂H₆ vs. heliocentric distance, the dotted lines are the derived mean values.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1571fig9.eps} \end{figure}$ Figure 9: Temperature ranges for the formation processes of C₂H₂, C₂H₆ and C₃H₄. The numbers in the boxes are referenced in the text. 1 and 2 denote areas with formation on grain surfaces (the solid part in box 2 is less effective than the dotted part), 3, 5, and 6 denote formation in the gas-phase. 4 shows an enrichment by trapping in amorphous water ice. The dashed box shows the likely range of formation temperatures.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig2.eps} \end{figure}$	Figure 2: Water production rate (diamonds) estimated for the model input and water production rates (crosses) measured by Weaver et al. (1999b) and (stars) Dello Russo et al. (2000).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig3.eps} \end{figure}$	Figure 3: Flowchart for obtaining abundance ratios using the ComChem model.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{1571fig4.eps} \end{figure}$	Figure 4: Overview of the best fitting $\rm C_3$ profiles (triangles - sunward, diamonds - tailward, negative heliocentric distances denote preperihelion observations).
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$\begin{figure} \par\includegraphics[width=7cm,clip]{1571fig5.eps} \end{figure}$	Figure 5: Overview of the best fitting $\rm C_2$ profiles (triangles - sunward, diamonds - tailward, negative heliocentric distances denote preperihelion observations).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig6.eps} \end{figure}$	Figure 6: Evolution of abundance ratios over heliocentric distance.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1571fig7.eps} \end{figure}$	Figure 7: Evolution of abundance ratios relative to water and to carbon monoxide over heliocentric distance.
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All Figures