\begin{table}%t4
\caption{\label{carbon_reac_tab}The main reactions and their
reaction rates. The $\dagger$ marks reactions for which rate
coefficients have been derived in this work. Coefficients which have
been derived during this work are printed in bold, while previous estimates
for these coefficients are printed in italics.}
%\centering
\par
\begin{tabular}{lclclclclll}
\hline \hline
\multicolumn{3}{c}{Reactants} & $\longrightarrow$ & \multicolumn{5}{c}{Products} & Rate coefficent [s$^{-1}$] & Reference\\ 
\hline
\CH26   & + &   $h\nu$   & $\longrightarrow$ &~\CH25 & + &   H   & & &         3.28~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\CH26   & + &   $h\nu$   & $\longrightarrow$ &~\CH24 & + &   H$_2$   & & &         3.67~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}}\\
\CH26   & + &   $h\nu$   & $\longrightarrow$ & CH$_3$    & + &   CH$_3$  & & &         8.80~$\times$~$10^{-7}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\CH26   & + &   $h\nu$   & $\longrightarrow$ & CH$_2$    & + &   CH$_4$  & & &         2.22~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}} \\[1ex]
\CH25   & + &   $h\nu$   & $\longrightarrow$ &~\CH22 & + &   H$_2$   & + & H     &     1.00~$\times$~$10^{-6}$ & \citep[][ pers. comm.]{BoicePC} \\[1ex]
\CH24   & + &   $h\nu$   & $\longrightarrow$ &~\CH22 & + &   H$_2$   &  & &        2.40~$\times$~$10^{-5}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\CH24   & + &   $h\nu$   & $\longrightarrow$ &~\CH22 & + &   H   & + & H     &     2.30~$\times$~$10^{-5}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\CH24   & + &   $h\nu$   & $\longrightarrow$ & CH$_2$    & + &   CH$_2$  &  &  &           6.00~$\times$~$10^{-5}$ &  \protect{\citep{1992ApetSS.195....1H}} \\[1ex]
\CH22   & + &   $h\nu$   & $\longrightarrow$ & \chem{C_2}   & + &   H$_2$   & & &         2.74~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}}\\
\CH22   & + &   e   & $\longrightarrow$ & \chem{C_2}   & + &   H$_2$   & + &   e    &    1.90~$\times$~$10^{-8}$ & \citep{1988Comput.Phys.Commun} \\
\CH22   & + &   $h\nu$   & $\longrightarrow$ & \chem{C_2H}  & + &   H   & & &         1.02~$\times$~$10^{-5}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\CH22   & + &   e   & $\longrightarrow$ &~\C2H  & + &   H   & + &   e    &    1.90~$\times$~$10^{-8}$ & \citep{1988Comput.Phys.Commun} \\[1ex]
C$_2$H  & + &   $h\nu$   & $\longrightarrow$ & \chem{C_2}   & + &   H   &  & &        3.00~$\times$~$10^{-5}$ &  \protect{\citep{1992ApetSS.195....1H}} \\[1ex]
\chem{C_2} & + &   $h\nu$   & $\longrightarrow$ & C     & + &   C   & & &         1.40~$\times$~$10^{-7}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\chem{C_2} & + &   $h\nu$   & $\longrightarrow$ & C$_2^+$   & + &   e   &  &         &    9.10~$\times$~$10^{-7}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
\chem{C_2} & + &   e   & $\longrightarrow$ & C     & + &   C   & + &   e     &   9.43~$\times$~$10^{-10}$ & \citep{1988Comput.Phys.Commun} \\[1.5ex]
\CH34   & + &   $h\nu$   & $\longrightarrow$ &~\CH33 & + &   H   & & &             1.33~$\times$~$10^{-4}$ & \citet[][ pers. comm.]{MosesPC} \\
\CH34   & + &   $h\nu$   & $\longrightarrow$ &~\CH32 & + &   H$_2$   & & &         2.96~$\times$~$10^{-5}$ & \citet[][ pers. comm.]{MosesPC} \\
\CH34   & + &   e   & $\longrightarrow$ & C$_3$ & + &   H$_2$   & + & H$_2$ + e & 3.80~$\times$~$10^{-8}$ & \citep{1988Comput.Phys.Commun} \\[1ex]
\CH33   & + &   $h\nu$   & $\longrightarrow$ &~\CH32 & + &   H   & & &         1.82~$\times$~$10^{-3}$ & \citet[][ pers. comm.]{MosesPC} \\[1ex]
$\dagger$~\CH32   & + &   $h\nu$   & $\longrightarrow$ & C$_3$ & + &   H$_2$   & & &             {\bf 9.50~$\times$~$10^{-7}$} & Helbert [this work] \\[.5ex]
\CH32 & + &   $h\nu$   & $\longrightarrow$ & C$_3$ & + &   H$_2$   & & &             {\it 1.9~$\times$~$10^{-6}$} &  \citet[][ pers. comm.]{MosesPC} \\[1ex]
$\dagger$ \chem{C_3} & + &   $h\nu$   & $\longrightarrow$ & \chem{C_2}   & + &   C   & & &         {\bf 2.00~$\times$~$10^{-5}$} & Helbert [this work] \\[.5ex]
\chem{C_3}   & + &   $h\nu$   & $\longrightarrow$ & \chem{C_2}   & + &   C   & & &         {\it 1.00~$\times$~$10^{-4}$} &    \protect{\citep{1992ApetSS.195....1H}} \\[1.5ex]
CH$_4$  & + &   $h\nu$   & $\longrightarrow$ & CH$_3$    & + &   H   & & &         2.64~$\times$~$10^{-7}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
CH$_4$  & + &   e   & $\longrightarrow$ & CH$_3$    & + &   H   & + &   e    &    9.43~$\times$~$10^{-10}$ & \citep{1988Comput.Phys.Commun} \\
CH$_4$  & + &   $h\nu$   & $\longrightarrow$ & CH$_2$    & + &   H$_2$   & & &         5.44~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
CH$_4$  & + &   $h\nu$   & $\longrightarrow$ & CH$_2$    & + &   H   & + &     H &     2.14~$\times$~$10^{-6}$ &  \protect{\citep{1992ApetSS.195....1H}} \\
CH$_4$  & + &   $h\nu$   & $\longrightarrow$ & CH    & + &   H$_2$   & + &     H &     6.39~$\times$~$10^{-7}$ &  \protect{\citep{1992ApetSS.195....1H}} \\[1ex]
CH$_2$  & + &   $h\nu$   & $\longrightarrow$ & CH    & + &   H   &  & &        2.00~$\times$~$10^{-5}$ & \protect{\citep{1992ApetSS.195....1H}} \\[1ex]
CH  & + &   $h\nu$   & $\longrightarrow$ & C     & + &   H   &   &       & 4.16~$\times$~$10^{-3}$ &  \protect{\citep{1992ApetSS.195....1H}} \\[1.5ex]
CH$_3$CN & + &  $h\nu$   & $\longrightarrow$ & CH$_3$    & + &   CN      & & &         5.00~$\times$~$10^{-5}$ & \protect{\citep{1992ApetSS.195....1H}} \\
CH$_3$CN & + &  e   & $\longrightarrow$ & CH$_3$    & + &   CN  & + &   e    &    3.80~$\times$~$10^{-8}$ &  \protect{\citep{1988Comput.Phys.Commun}} \\
\hline
\end{tabular}
\end{table}