\begin{table}%t3
\caption{Calculated and observed column densities (cm$^{-2}$) in $\zeta$ Persei.}\label{obs}
%\centering
\par
\begin{tabular}{l|ccc|cc}
\hline  \hline
Species      & Diffuse Phase   & Dense Phase & Total   &
\multicolumn{2}{c}{Observation} \\
     \hline
H$^{(1)}$            & 3.5(20) & 1.4(17)     & 3.5(20) & 5.7(20) & 7.1(20)   \\
H$_2$$^{(2)}$        & 4.5(20) & 1.1(19)     & 4.6(20) & 3.2(20) & 7.1(20)   \\
HD$^{(3)}$           & 1.5(16) & 3.9(13)     & 1.5(16) & 2.0(15) & 1.1(16)   \\
C$^+$$^{(4)}$        & 1.6(17) & 1.2(15)     & 1.6(17) & 1.8(17) &          \\
C$^{(3)}$            & 1.4(15) & 1.6(15)     & 2.8(15) & 2.9(15) & 3.6(15)   \\
CO$^{(5)}$           & 3.5(14) & 7.9(13)     & 4.2(14) & 5.4(14) & --         \\
CH$^{(6)}$           & 2.4(12) & 5.6(12)     & 8.0(12) & 1.9(13) & 2.0(13)   \\
CH$^+$$^{(7)}$       & 2.2(10) & 2.7(08)     & 2.2(10) & 3.5(12) & --         \\
C$_2$$^{(8)}$        & 1.9(11) & 1.9(13)     & 1.9(13) & 1.6(13) & 2.2(13)   \\
C$_3$$^{(9)}$        & 3.1(08) & 2.1(12)     & 2.1(12) & 1.0(12) &           \\
CN$^{(10)}$          & 6.6(10) & 1.9(12)     & 1.9(12) & 2.7(12) & 3.3(12)   \\
NH$^{(11)}$          & 3.5(11) & 1.2(09)     & 3.5(11) & 9.0(11) &   --       \\
O$^{(12)}$           & 4.0(17) & 7.2(15)     & 4.0(17) & 0.2(18) & 1.0(18)   \\
OH $^{(13)}$         & 4.9(13) & 1.1(09)     & 4.9(13) & 4.0(13) &   --       \\
H$_3^+$$^{(14)}$     & 2.9(13) & 5.0(09)     & 2.9(13) & 8.0(13) &   --       \\
S$^{+}$$^{(3)}$      & 2.3(16) & 4.1(14)     & 2.3(16) & 1.7(16) & 2.3(16)   \\
S$^{(3)}$            & 3.7(13) & 1.0(13)     & 4.7(13) & 1.5(13) & 2.2(13)   \\
Si$^+$$^{(3)}$       & 3.6(16) & 6.5(14)     & 3.6(16) & 2.8(16)  &
6.6(16)    \\
H$_2$ ($J$~=~0)$^{(2)}$& 3.0(20) & 1.1(19)     & 3.0(20) & 2.2(20) & 4.8(20)   \\
H$_2$ ($J$~=~1)$^{(2)}$& 1.5(20) & 1.8(17)     & 1.5(20) & 1.0(20) & 2.3(20)   \\
H$_2$ ($J$~=~2)$^{(3)}$& 1.9(17) & 4.7(13)     & 2.0(17) & 1.1(18) & 2.4(18)   \\
H$_2$ ($J$~=~3)$^{(3)}$& 3.9(15) & 2.8(13)     & 3.9(15) & 2.0(16) & 9.6(16)   \\
H$_2$ ($J$~=~4)$^{(3)}$& 3.0(14) & 2.5(13)     & 3.2(14) & 1.1(15) & 2.0(15)   \\
H$_2$ ($J$~=~5)$^{(3)}$& 1.2(14) & 8.0(12)     & 1.3(14) & 2.3(14) & 2.8(14)   \\
    \hline
Ionization fraction& 2.2(--4) & 1.0(--04)    &         &         &          \\
Length             & 4.2 pc  & 76 AU &         &         &          \\
$A_{\rm V}$     & 0.69    & 0.013       & 0.70    &         &          \\
\hline
\noalign{\smallskip}
\multicolumn{6}{l}{1 Bohlin (\cite{Bohlin75}).}   \\
\multicolumn{6}{l}{2 Savage et~al. (\cite{Savage77}).}   \\
\multicolumn{6}{l}{3 Snow (\cite{Snow77}) but upper limits reanalyzed here with updated $f$~values (see text)}\\
\multicolumn{6}{l}{$\;\;$for H$_{2}$ $J \ge 2$ and for HD using $b=$ 2.5~km~s$^{-1}$.}   \\
\multicolumn{6}{l}{4 Cardelli et~al. (\cite{cardelli96}).}   \\
\multicolumn{6}{l}{5 Snow (\cite{Snow77}), with updated $f$-values from van~Dishoeck \& Black (\cite{vanD86}).}   \\
\multicolumn{6}{l}{6 Jura \& Meyer (\cite{Jura85}).}   \\
\multicolumn{6}{l}{7 Federman (\cite{Fed82}).}   \\
\multicolumn{6}{l}{8 Danks \& Lambert (\cite{Danks83}) -- reanalyzed by van~Dishoeck \& Black (\cite{vanD89}).}   \\
\multicolumn{6}{l}{9 Maier et~al. (\cite{Mai01}).}   \\
\multicolumn{6}{l}{10 Meyer \& Jura (\cite{Meyer85}).}   \\
\multicolumn{6}{l}{11 Meyer \& Roth (\cite{Meyer91}).}   \\
\multicolumn{6}{l}{12 van~Dishoeck \& Black (\cite{vanD86}).}   \\
\multicolumn{6}{l}{13 Felenbok \& Roueff (\cite{Fel96}).}   \\
\multicolumn{6}{l}{14 McCall et~al. (\cite{McCall03}).}
\end{tabular}
\end{table}