\begin{table}%T2
 \caption{\label{dis.tab}Quantities relevant to PAH survival.   }
\small%\centering
\par
\begin{tabular}{c r c c c c  r r r r }
  \hline\hline\noalign{\smallskip}
  &  (1) &   (2) & (3)  &    (4)   & (5) &  (6)  &(7) &(8) &(9) \\
\hline
 \noalign{\smallskip}
  component &$h\overline{\nu}$& $\kappa$ & $\eta$ & ${K/K_{\rm V}}$& $x$ 
  &$z_0/H$&$\ell/H$ 
  & $t_{\rm abs}$ & $v_{\rm cr}$ \\ 
  & eV & $10^{-4}$~\AA$^2$ & & & & &&  & m/s \\
  %\hline
  photosphere & 2.7& 700 &$\ll$$1$ & 1.2 & --  & 4.4 &0.5& 5 s  & -- \\
  FUV         & 4.2& 700&$\ll$$1$ & 1.5 & --  & 4.5 &0.5&  120 s  & -- \\
  EUV         & 97       & 36  &$\sim$0.5&110 & 9   &5.3&0.4&9~days&2900 \\
  X-ray      & 1100  & 0.17 &$\ll$$1$& 0.55 &100 & 4.2 &0.5& 290~yr &3.4 \\
  \hline
\end{tabular}
\tablefoot{$z_0, \ell, t_{\rm abs}$ and $v_{\rm cr}$ refer
to $r=10$~AU.\\
(1) The mean energy of destructive photons $h\overline{\nu}$ from
Eq.~(\ref{hnu_mean}) at the bottom of the extinction layer (see
Fig.~\ref {zdisk.ps}); for photospheric and FUV photons we put
$\nu_{\rm c} =0$ and for EUV and X-rays we integrate for $\nu \geq
\nu_{\rm c}$ (Eq.~(\ref{Stabil2})); 
 (2) absorption cross section $\kappa$ per C atom at a 
frequency $\overline{\nu}$;  
 (3)~approximate mean degree of ionization of the gas in
the extinction layer ; 
 (4) extinction cross section of gas and dust at frequency
$\overline\nu$ normalized to $K_{\rm V}= 200$~cm$^2$~g$^{-1}$; 
 (5) number of expelled atoms $x$ per absorption event
from Eq.~(\ref{x_Atome}); 
 (6) altitude of the bottom of the extinction layer in
units of the scale height $H$; 
 (7) thickness of extinction layer; 
 (8) mean time $t_{\rm abs}$ from Eq.~(\ref{t_abs}) in
which one photon is absorbed; 
 (9) critical vertical velocity for PAH survival.}
 \vspace*{4mm}
\end{table}