\begin{table}%t2
%
\par
\caption{\label{table2}The reaction rates for the VUV photolysis of Py:H$_2$O ($\sim$1:5000) ice at 25~K compared to those for 4-methylypyrene:H$_2$O (1:$>$500) ice at 15~K \citep{gudipati03}.}
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\par
\small 
\par
$$\begin{tabular}{l c r@{~$\times$~}l c c}
\hline \hline \noalign{\smallskip}
\multicolumn{2}{c}{Rate}&\multicolumn{2}{c}{This work}&Photon rate\tablefootmark{a}& Gudipati (2003)\\
&&\multicolumn{2}{c}{(s$^{-1}$)}&(cm$^2$~photon$^{-1}$)&(s$^{-1}$)\\
\hline\noalign{\smallskip}
Py$\stackrel{\rm VUV}{\longrightarrow}$ Py$^{\cdot+}$ &($k_{11}$)&(1.2 $\pm$ 0.1)&10$^{-3}$&	1.2 $\times$ 10$^{-17}$	&1.3 $\times$ 10$^{-3}$\\
Py$^{\cdot+}$+e$^{-}\rightarrow$Py & ($k_{12}$)&(9 $\pm$ 2)&10$^{-4}$&	9 $\times$ 10$^{-18}$	&8 $\times$ 10$^{-4}$\\
Py $\rightarrow$ P$_1$& ($k_1$)&(5 $\pm$ 1)& 10$^{-5}$&...&4  $\times$  10$^{-5}$\\
Py$^{\cdot+}$ $\rightarrow$ P$_2$& ($k_2$)&(5 $\pm$ 1)&10$^{-4}$&...
&5 $\times$ 10$^{-5}$\\
\hline
\end{tabular}$$
\tablefoot{\tablefoottext{a}{Photon rates are indicated only for reaction channels which are dominated by photon processes.}}
\end{table}