\begin{table}%t3
\caption{\label{irradspecies}Infrared absorption bands of the species formed upon VUV
irradiation of a NH$_3$:CO$_2$ ice at 10 K.}
\par
%\centerline
 {
\begin{tabular}{lllll}
\hline\hline \multicolumn{1}{l}{Wavenumbers}&\multicolumn{1}{c}{Species}&\multicolumn{1}{c}{Assigment}& \multicolumn{1}{c}{Band Strength
}\\
(cm$^{-1}$) &  &   & (cm~molecule$^{-1}$)  \\
\hline
2164 (w) & OCN$^{-~a}$ & ($\nu_{3}$) $\nu_{\rm as}$~(NCO)  &$1.30\times10^{-16}$\\
2140 (vs) & CO $^{b}$ & ($\nu_1$)~$\nu$~C=O  &$1.10\times10^{-17}$ \\
1694 (vw) & NH$_{2}$COOH dimer $^{c}$ & $\nu$ C=O  &$5\times10^{-18}$\\
1590 (m) & [HCOO$^{-}$][NH$_{4}^{+}$] $^{d, e}$ & $\nu_{\rm as}$(COO$^{-}$)  &$1.0\times10^{-16}$ \\
1548 (m) & [NH$_2$COO$^{-}$][NH$_{4}^{+}$] $^{c}$ & $\nu_{\rm as}$(COO$^{-}$)  &$2\times10^{-17}$ \\
1501 (s) &  [HCOO$^{-}$][NH$_{4}^{+}$] $^{d, e}$ & $\delta_{\rm s}$ (NH$_{4}^{+}$)   & \\
1389 (w) &  [HCOO$^{-}$][NH$_{4}^{+}$] $^{d, e}$ & $\delta_{\rm s}$ (CH)  &$8.0\times10^{-18}$\\
1330 (w) & [HCOO$^{-}$][NH$_{4}^{+}$] $^{d, e}$ & $\nu_{\rm s}$(COO$^{-}$)&$1.7\times10^{-17}$\\
1319 (w) & NH$_{2}$COOH dimer $^{c}$ & &\\
1240 (vw) & ? & ? &  \\
\hline
\end{tabular}}
\medskip
\par
References. $^a$ Raunier (2003); $^b$ Gerakines (1995); $^c$ this work; \\ $^d$ Hudson (2000); $^e$ Schutte (1999).\\
Vibration mode: stretching ($\nu$), bending ($\delta$).\\
Indication: asymmetric (as), symmetric (s). \\
Intensities: very strong (vs), strong (s), medium (m), weak (w) and very weak (vw).
\end{table}