\begin{table}%t1
\caption{\label{exps}UHV ice-segregation experiments.}           
%\centerline
{\small
\begin{tabular}{l c c c c c  }        
\hline\hline                
Exp. &CO$_2$/CO&H$_2$O:X &Thick. (ML) & $T_{\rm dep}$ (K) &$T_{\rm exp}$ (K) \\ 
\hline            % inserts double horizontal lines
1 &CO$_2$ &10:1 &37 &19 &60 \\ 
2 &CO$_2$ &3:1 &36 &19 &60 \\  
3 &CO$_2$ &2:1 &8 &19 &53 \\   
4 &CO$_2$ &2:1 &8 &19 &58 \\   
5 &CO$_2$ &2:1 &11 &19 &50 \\  
6 &CO$_2$ &2:1 &11 &19 &55 \\  
7 &CO$_2$ &2:1 &11 &19 &60 \\  
%8 &CO$_2$ &2:1 &12 &20 &60 \\ 
8 &CO$_2$ &2:1 &13 &19 &50 \\  
9 &CO$_2$ &2:1 &18 &19 &55 \\  
10 &CO$_2$ &2:1 &18 &19 &60 \\ 
11 &CO$_2$ &2:1 &20 &19 &53 \\ 
12 &CO$_2$ &2:1 &27 &19 &56 \\ 
13 &CO$_2$ &2:1 &30 &19 &50 \\ 
14 &CO$_2$ & 2:1 &17 &40 &55 \\
15 &CO$_2$ &2:1 &21& 50 &55 \\             
16$^{a}$ &CO$_2$ &2:1 &10 &19 &55 \\   
17$^{b}$ &CO$_2$ &2:1 &9/75 &19 &53 \\ 
18 &CO$_2$ &1:1 &13 &19 &50 \\             
19 &CO$_2$ &1:1 &13 &19 &55 \\             
20 &CO &2:1 &22 &19 &27 \\ 
21 &CO &1:1 &10 &16 &27 \\ 
22 &CO &1:1 &32 &19 &23 \\ 
23 &CO &1:1 &31 &19 &25 \\ 
24 &CO &1:1 &29 &19 &27 \\ 
\hline
\end{tabular}}
\par
\medskip
$^{a}$~The ice was annealed at 60~K for less than a minute before cooled back to the segregation temperature.\\ $^{b}$~The H$_2$O:CO$_2$ ice mixture of 9~ML was deposited on top of 75~ML H$_2$O ice. The H$_2$O ice was deposited at 100~K to achieve a compact ice substrate and then cooled to 19~K before depositing the ice mixtures.
\end{table}