\begin{table}%t3
\caption{\label{tab:SIG-Destruct}Dissociation cross-sections of the studied molecular species for radiolysis of ammonia-containing ices by 46~MeV~Ni ions.} 
%\centerline
 {
 \small \begin{tabular}{ l l c c c c c c }
\hline \hline\noalign{\smallskip}
Species  & Mixture & $\sigma_{\rm d}$  & $N_\infty$  & $Y$   &  $L^f$ &  $N_0$   & Model    \\
& (H$_2$O:NH$_3$:CO) & $(10^{-13}$~cm$^2$)  & (10$^{17}$~molec~cm$^{-2}$)  & (10$^4$ molec ion$^{-1}$)  & (10$^4$~molec~ion$^{-1}$) & (10$^{17}$ molec~cm$^{-2}$)   &    \\
\hline
H$_2$O   & (1:0.5:0)     & $\sim$2  & 23        & 1$^a$    & 38    & 29      & 1 \\
&  (1:0.6:0.4)  & $\sim$2  & 19        & 1$^a$    & 35    & 24      & 2 \\
NH$_3$   & (1:0.5:0)     & 1.3       & NA$^e$    & 0$^b$    & 0      & 2.0     & 3 \\
& (1:0.6:0.4)   & 1.4       & NA        & 0$^b$    & 0      & 1.7     & 4 \\
CO       & (1:0.6:0.4)   & 1.9       & NA        & 0$^b$    & 0      & 1.0     & 5a \\
& (1:0.6:0.4)   & 1.9       & NA        & 0$^b$    & 1$^d$  & 1.0     & 5b \\
& (1:0.6:0.4)   & 1.9       & NA        & 1$^c$    & 0      & 1.0     & 5c\\
\hline  
\end{tabular}}
\medskip
$^a$ Taken from Brown et~al. (\cite{Brown1984}); $^b$~no sputtering. Assuming that the water layering is thick enough to fully cover the NH$_3$ or CO molecules on the surface; $^c$~assuming that there is no water layering and considering a sputtering of $1 \times 10^4$~molec~ion$^{-1}$ (the same adopted for water molecules), $^d$~assuming an extra source of CO for layering; $^e$ NA=Not applied; $^f$~for H$_2$O: derived from $L = N_\infty \sigma_{\rm d}+Y$. For NH$_3$ and CO: assuming no layering (except model~5b).
\end{table}