\begin{table}
\caption{Adiabatic and vertical ionisation energies (in eV) of each PAH in 
our sample evaluated at the \mbox{B3LYP/6$-$31+G$^\star$} level of theory. 
Whenever available, we list laboratory data for comparison. The experimental 
single IEs come from the NIST Chemistry WebBook \citep{lia05} while second and 
double IEs are, respectively, from charge stripping and photon-impact 
measurements of \citet{sch01} for corannulene and coronene and from 
\citet{tob94} in all the other cases. According to our calculations the 
dication electronic ground-states are marked in boldface. \label{double}}
\begin{tabular}{cc ccc ccc ccc|cc}
\hline \hline
PAH & \multicolumn{3}{c}{First IE ($I^+$)} & Dication & 
\multicolumn{3}{c}{Second IE ($\Delta I$)} & \multicolumn{3}{c|}
{Double IE ($I^{++}$)}&&\\
molecule & Adiab. & Vert. & Exp. & state & Adiab. & 
Vert. & Exp. & Adiab. & Vert. & Exp. & $I^+_{\rm V} 
+ \Delta I_{\rm V}$ & $I^{++}_{\rm V}$ $-${} ($I^+_{\rm V} + \Delta I_{\rm V}$)\\
\hline
Azulene & 
\multirow{2}*{7.15} & \multirow{2}*{7.27} & \multirow{2}*{7.42~$\pm$~0.02} & 
{\bf singlet} & {\bf 12.77} & {\bf 12.87} & \multirow{2}*{--} & 
{\bf 19.92} & {\bf 20.34} & \multirow{2}*{--} & {\bf 20.14} & {\bf + 0.20} \\
(C$_{10}$H$_{8}$) & & & & triplet & 13.39 & 13.53 & & 20.54 & 20.63 & & 20.80 
& $-${} 0.17 \\
\hline
Naphthalene &  
\multirow{2}*{7.80} & \multirow{2}*{7.89} & 
\multirow{2}*{8.144~$\pm$~0.001} & {\bf singlet} & {\bf 13.19} & {\bf 13.28} & 
\multirow{2}*{14.6~$\pm$~0.5} & {\bf 20.99} & {\bf 21.35} & 
\multirow{2}*{21.5~$\pm$~0.2} & {\bf 21.17} & {\bf + 0.18}\\
(C$_{10}$H$_{8}$) & & & & triplet & 13.65 & 13.77 & & 21.45 & 21.57 & & 21.66 
& $-${} 0.09\\
\hline
Acenaphtylene &  
\multirow{2}*{7.66} & \multirow{2}*{7.86} & 
\multirow{2}*{8.12~$\pm$~0.10} & singlet & 12.81 & 13.06 & \multirow{2}*{--} 
& 20.48 & 21.32 & \multirow{2}*{21.4~$\pm$~0.2} & 20.92 & + 0.39\\
(C$_{12}$H$_{8}$) & & & & {\bf triplet} & {\bf 12.78} & {\bf 12.88} & & 
{\bf 20.45} & {\bf 20.66} & & {\bf 20.74} & {\bf $-${} 0.08} \\
\hline
Biphenylene &  
\multirow{2}*{7.22} & \multirow{2}*{7.37} & 
\multirow{2}*{7.58~$\pm$~0.03} & {\bf singlet} & {\bf 12.09} & {\bf 
12.26} & 
\multirow{2}*{--} & {\bf 19.31} & {\bf 19.94} & 
\multirow{2}*{19.7~$\pm$~0.2} & 
{\bf 19.63} & {\bf + 0.31}\\
(C$_{12}$H$_{8}$)& & & & triplet & 13.23 & 13.31 & & 20.45 & 20.61 & & 
20.68 & $-${} 0.08 \\
\hline
Acenaphthene &  
\multirow{2}*{7.37} & \multirow{2}*{7.46} & 
\multirow{2}*{7.75~$\pm$~0.05} & {\bf singlet} & {\bf 12.42} & {\bf 12.51}& 
\multirow{2}*{--}& {\bf 19.78} & {\bf 20.17} & \multirow{2}*{21.7~$\pm$~0.2} & 
{\bf 19.97}& {\bf + 0.20}\\
(C$_{12}$H$_{10}$) & & & & triplet & 13.22 & 13.35 & & 20.59 & 20.72 & & 20.81 
& $-${} 0.09 \\
\hline
Fluorene &  
\multirow{2}*{7.56} & \multirow{2}*{7.69} & 
\multirow{2}*{7.91~$\pm$~0.02} & {\bf singlet} & {\bf 12.39} & {\bf 12.52} & 
\multirow{2}*{--} & {\bf 19.96} & {\bf 20.47} & \multirow{2}*{21.0~$\pm$~0.2} & 
{\bf 20.22}& {\bf + 0.26}\\ 
(C$_{13}$H$_{10}$) & & & & triplet & 12.86 & 12.99 & & 20.43 & 20.59 & & 20.68 
& $-${} 0.09 \\
\hline
Anthracene &  
\multirow{2}*{7.02} & \multirow{2}*{7.09} & 
\multirow{2}*{7.439~$\pm$~0.006} & {\bf singlet} & {\bf 11.68} & {\bf 11.74} & 
\multirow{2}*{--} & {\bf 18.70} & {\bf 18.95} & \multirow{2}*{--} & 
{\bf 18.83} & {\bf + 0.12}\\ 
(C$_{14}$H$_{10}$) & & & & triplet & 12.68 & 12.77 & & 19.70 & 19.80 & & 19.86 &
$-${} 0.06\\
\hline
Phenanthrene &  
\multirow{2}*{7.53} & \multirow{2}*{7.63} & 
\multirow{2}*{7.891~$\pm$~0.001} & {\bf singlet} & {\bf 12.11} & {\bf 12.23}
& \multirow{2}*{--} & {\bf 19.63} & {\bf 20.08} & \multirow{2}*{--} & 
{\bf 19.86}& {\bf + 0.22}\\ 
(C$_{14}$H$_{10}$) & & & & triplet & 12.19 & 12.32 & & 19.72 & 19.86 & & 19.96 &
$-${} 0.09 \\
\hline
Pyrene &  
\multirow{2}*{7.07} & \multirow{2}*{7.14} & 
\multirow{2}*{7.426~$\pm$~0.001} & {\bf singlet} & {\bf 11.57} & {\bf 11.64} & 
\multirow{2}*{14.4~$\pm$~0.5} & {\bf 18.63} & {\bf 18.92} & 
\multirow{2}*{19.8~$\pm$~0.2} & {\bf 18.78} & {\bf + 0.14}\\ 
(C$_{16}$H$_{10}$) & & & & triplet & 12.28 & 12.39 & & 19.35 & 19.44 & & 19.53 &
$-${} 0.09 \\
\hline
Tetracene &  
\multirow{2}*{6.49} & \multirow{2}*{6.55} & 
\multirow{2}*{6.97~$\pm$~0.05} & {\bf singlet} & {\bf 10.66} & {\bf 10.70} & 
\multirow{2}*{13.1~$\pm$~0.5} & {\bf 17.15} & {\bf 17.34} & 
\multirow{2}*{18.6~$\pm$~0.2} & {\bf 17.25} & {\bf + 0.09}\\ 
(C$_{18}$H$_{12}$) & & & & triplet & 11.47 & 11.55 & & 17.96 & 18.11 & & 18.10 &
+ 0.01 \\
\hline
Chrysene &  
\multirow{2}*{7.17} & \multirow{2}*{7.25} & 
\multirow{2}*{7.60~$\pm$~0.01} & {\bf singlet} & {\bf 11.28} & {\bf 11.37} & 
\multirow{2}*{--} & {\bf 18.45} & {\bf 18.78} & \multirow{2}*{--} & 
{\bf 18.63} & {\bf + 0.16}\\ 
(C$_{18}$H$_{12}$) & & & & triplet & 11.67 & 11.75 & & 18.84 & 18.94 & & 19.01 &
$-${} 0.06\\
\hline
Benz[a]anthracene &  \multirow{2}*{6.98} & 
\multirow{2}*{7.05} & \multirow{2}*{7.45~$\pm$~ 0.05} & {\bf singlet} & 
{\bf 11.16} & {\bf 11.24} & \multirow{2}*{--} & {\bf 18.14} & {\bf 18.42} & 
\multirow{2}*{--} & {\bf 18.29} & {\bf + 0.13}\\ 
(C$_{18}$H$_{12}$) & & & & triplet & 11.35 & 11.45 & & 18.33 & 18.48 & & 
18.50 & $-${} 0.02\\
\hline
Triphenylene &  
\multirow{2}*{7.52} & \multirow{2}*{7.86} & 
\multirow{2}*{7.87~$\pm$~0.02} & singlet & 11.72 & 11.81 & \multirow{2}*{--} & 
19.24 & 19.59 & \multirow{2}*{--} & 19.67 & $-${} 0.08\\ 
(C$_{18}$H$_{12}$) & & & & {\bf triplet} & {\bf 11.57} & {\bf 11.65} & & 
{\bf 19.09} & {\bf 19.20} & & {\bf 19.51} & {\bf $-${} 0.31} \\
\hline
Corannulene &  
\multirow{2}*{7.62} & \multirow{2}*{7.73} & \multirow{2}*{7.83~$\pm$~0.02} & 
singlet & 12.02 & 12.15 & \multirow{2}*{13.8~$\pm$~0.3}
& 19.63 & 20.14 & \multirow{2}*{20.1~$\pm$~0.2} & 19.88 & + 0.26 \\ 
(C$_{20}$H$_{10}$) & & & & {\bf triplet} & {\bf 11.66} & {\bf 11.76} & 
& {\bf 19.28} & {\bf 19.50} & & {\bf 19.49} & {\bf + 0.01} \\
\hline
Benzo[a]pyrene &  \multirow{2}*{6.71} & 
\multirow{2}*{6.78} & \multirow{2}*{7.12~$\pm$~0.01} & {\bf singlet} & 
{\bf 10.75} & {\bf 10.82} & \multirow{2}*{--} & {\bf 17.46} & 
{\bf 17.73} & \multirow{2}*{--} & {\bf 17.60} & {\bf +0.13}\\ 
(C$_{20}$H$_{12}$) & & & & triplet & 11.47 & 11.58 & & 18.18 & 18.30 & 
& 18.36 & $-$0.06\\
\hline
Benzo[e]pyrene &  
\multirow{2}*{7.05} & \multirow{2}*{7.12} & 
\multirow{2}*{7.43~$\pm$~0.04} & {\bf singlet} & {\bf 11.20} & {\bf 11.26} & 
\multirow{2}*{--} & {\bf 18.25} & {\bf 18.51} & 
\multirow{2}*{--} & {\bf 18.38} & {\bf + 0.13}\\ 
(C$_{20}$H$_{12}$) & & & & triplet & 11.34 & 11.42 & & 18.38 & 18.52 & 
& 18.54 & $-$0.02\\
\hline
Perylene &  
\multirow{2}*{6.57} & \multirow{2}*{6.64} & 
\multirow{2}*{6.960~$\pm$~0.001} & {\bf singlet} & {\bf 10.62} & {\bf 
10.68} & \multirow{2}*{--} & {\bf 17.19} & {\bf 17.46} & 
\multirow{2}*{18.0~$\pm$~0.2} & {\bf 17.33} & {\bf + 0.14}\\ 
(C$_{20}$H$_{12}$) & & & & triplet & 12.03 & 12.11 & & 18.60 & 18.73 & & 18.75 &
$-$0.02\\
\hline
Anthanthrene &  
\multirow{2}*{6.46} & \multirow{2}*{6.52} & 
\multirow{2}*{6.92~$\pm$~0.04} & {\bf singlet} & {\bf 10.43} & {\bf 10.48} & 
\multirow{2}*{--} & {\bf 16.90} & {\bf 17.10} & \multirow{2}*{--} & 
{\bf 17.00} & {\bf + 0.10} \\ 
(C$_{22}$H$_{12}$) & & & & triplet & 11.38 & 11.54 & & 18.01 & 18.09 & & 
18.06 & +0.03 \\
\hline
Benzo[g,h,i]perylene &  \multirow{2}*{6.79} & 
\multirow{2}*{6.86} & \multirow{2}*{7.17~$\pm$~0.02} & {\bf singlet} & 
{\bf 10.74} & {\bf 10.80} & \multirow{2}*{--} 
& {\bf 17.53} & {\bf 17.78} & \multirow{2}*{--} & {\bf 17.65} & {\bf + 0.13}\\
(C$_{22}$H$_{12}$) & & & & triplet & 11.19 & 11.28 & & 17.98 & 18.09 & & 18.14
& $-${} 0.05\\
\hline
Pentacene &  
\multirow{2}*{6.12} & \multirow{2}*{6.16} & 
\multirow{2}*{6.63~$\pm$~0.05} & {\bf singlet} & {\bf 9.91} & {\bf 9.94} & 
\multirow{2}*{12.8~$\pm$~0.5} & {\bf 16.03} & {\bf 16.18} & 
\multirow{2}*{17.4~$\pm$~0.2} & {\bf 16.11} & {\bf + 0.07} \\ 
(C$_{22}$H$_{14}$) & & & & triplet & 10.56 & 10.63 & & 16.67 & 16.79 & & 16.79
& 0.00 \\
\hline
Coronene &  \multirow{2}*{7.02} & 
\multirow{2}*{7.08} & \multirow{2}*{7.29~$\pm$~0.03} & singlet & 10.87 & 
10.92 & \multirow{2}*{12.8~$\pm$~0.3} & 17.88 & 18.11 & 
\multirow{2}*{18.5~$\pm$~0.2} & 18.00 & + 0.11 \\ 
(C$_{24}$H$_{12}$) & & & & {\bf triplet} & {\bf 10.72} & {\bf 10.79} & 
& {\bf 17.74} & {\bf 17.80} & & {\bf 17.87} & {\bf $-$0.06}\\
\hline
Dibenzo[b,def]crysene &  
{6.39} & {6.45} & 
{6.82} & {\bf singlet} & {\bf 10.11} & {\bf 10.17} & 
 {--} & {\bf 16.50} & {\bf 16.73} & {--}& 
{\bf 16.62} & {\bf + 0.11} \\ 
(C$_{24}$H$_{14}$) & & & & triplet & 11.00 & 11.06 & & 17.39 & 17.51 & & 17.51
& 0.00 \\
\hline
Dibenzo[cd,lm]perylene &  
\multirow{2}*{6.31} & \multirow{2}*{6.38} & 
\multirow{2}*{6.72~$\pm$~0.02} & {\bf singlet}& {\bf 9.88} & {\bf 9.94} & 
\multirow{2}*{--} & {\bf 16.20} & {\bf 16.45} & \multirow{2}*{--} & 
{\bf 16.32} & {\bf + 0.13} \\ 
(C$_{26}$H$_{14}$) & & & & triplet & 11.03 & 11.12 & & 17.35 & 17.43 & & 
17.50 & $-${} 0.07\\
\hline
Hexacene &  
\multirow{2}*{5.83} & \multirow{2}*{5.87} & \multirow{2}*{6.36~$\pm$~0.02} & {\bf singlet} & {\bf 9.34} & {\bf 9.37} & \multirow{2}*{--}  
& {\bf 15.18} & {\bf 15.30} & \multirow{2}*{--} & {\bf 15.24} & {\bf +0.06}\\
(C$_{26}$H$_{16}$) & & & & triplet & 9.84 & 9.90 & & 15.68 & 15.78 & & 
15.78 & 0.00 \\
\hline
Bisanthene &  
\multirow{2}*{5.85} & \multirow{2}*{5.90} & \multirow{2}*{6.30} & 
{\bf singlet} & {\bf 9.47} & {\bf 9.51} & \multirow{2}*{--}  
& {\bf 15.33} & {\bf 15.48} & \multirow{2}*{--} & {\bf 15.40} & {\bf + 0.08}\\
(C$_{28}$H$_{14}$) & & & & triplet & 10.69 & 10.76 & & 16.54 & 16.70 & & 16.66 &
+ 0.04 \\
\hline
Benzo[a]coronene &  \multirow{2}*{6.75} & 
\multirow{2}*{6.81} & \multirow{2}*{7.08} & 
{\bf singlet} & {\bf 10.34} & {\bf 10.39} & \multirow{2}*{--}  
& {\bf 17.10} & {\bf 17.30} & \multirow{2}*{--} & {\bf 17.20} & {\bf + 0.10}\\
(C$_{28}$H$_{14}$) & & & & triplet & 10.46 & 10.52 & & 17.21 & 17.29 & & 17.33
& $-${} 0.04\\
\hline
Dibenzo[bc,kl]coronene &  
\multirow{2}*{6.01} & \multirow{2}*{6.05} & 
\multirow{2}*{6.42~$\pm$~0.02} & {\bf singlet} & {\bf 9.54} & {\bf 9.57} & 
\multirow{2}*{--} & {\bf 15.55} & {\bf 15.70} & 
\multirow{2}*{--} & {\bf 15.62} & {\bf + 0.08} \\ 
(C$_{30}$H$_{14}$) & & & & triplet & 10.19 & 10.27 & & 16.20 & 16.36 & 
& 16.32 & + 0.04 \\
\hline
Dibenzo[bc,ef]coronene &  
\multirow{2}*{6.12} & \multirow{2}*{6.17} & 
\multirow{2}*{6.50} & {\bf singlet} & {\bf 9.66} & {\bf 9.69} & 
\multirow{2}*{--} & {\bf 15.78} & {\bf 15.94} & \multirow{2}*{--} & 
{\bf 15.86} & {\bf + 0.08} \\ 
(C$_{30}$H$_{14}$) & & & & triplet & 10.67 & 10.78 & & 16.79 & 16.87 & & 16.95 
& $-$0.08 \\
\hline
Terrylene &  
\multirow{2}*{5.98} & \multirow{2}*{6.05} & 
\multirow{2}*{6.42~$\pm$~0.02} & {\bf singlet} & {\bf 9.33} & {\bf 9.38} & 
\multirow{2}*{--} & {\bf 15.31} & {\bf 15.55} & \multirow{2}*{--} & 
{\bf 15.43} & {\bf + 0.12} \\ 
(C$_{30}$H$_{16}$) & & & & triplet & 10.40 & 10.45 & & 16.38 & 16.49 & & 16.50 
& $-${} 0.01 \\
\hline
Ovalene &  
\multirow{2}*{6.36} & \multirow{2}*{6.41} & 
\multirow{2}*{6.71} & {\bf singlet} & {\bf 9.82} & {\bf 9.86} & 
\multirow{2}*{--} & {\bf 16.18} & {\bf 16.34} & 
\multirow{2}*{--} & {\bf 16.26} & {\bf + 0.08}\\ 
(C$_{32}$H$_{14}$) & & & & triplet & 10.30 & 10.35 & & 16.66 & 16.72 & 
& 16.76 & $-$0.04 \\
\hline
Tetrabenzo[bc,ef,kl,no]coronene &  
\multirow{2}*{5.41} & \multirow{2}*{5.44} & \multirow{2}*{--} & 
{\bf singlet} & {\bf 8.75} & {\bf 8.77} & \multirow{2}*{--}  
& {\bf 14.16} & {\bf 14.24} & \multirow{2}*{--} & 
{\bf 14.21} & {\bf + 0.03} \\ 
(C$_{36}$H$_{16}$) & & & & triplet & 9.66 & 9.72 & & 15.07 & 15.17 & & 
15.15 & + 0.02\\
\hline
Circumbiphenyl &  \multirow{2}*{6.46} & 
\multirow{2}*{6.52} & \multirow{2}*{6.81~$\pm$~0.02} & {\bf singlet} & 
{\bf 9.58} & {\bf 9.64} & \multirow{2}*{--}  
& {\bf 16.04} & {\bf 16.26} & \multirow{2}*{--} & {\bf 16.15} & 
{\bf + 0.11} \\ 
(C$_{38}$H$_{16}$) & & & & triplet & 9.70 & 9.75 & & 16.16 & 16.21 & & 
16.27 & $-$0.06\\
\hline
Circumanthracene &  
\multirow{2}*{5.90} & \multirow{2}*{5.94} & \multirow{2}*{--} & 
{\bf singlet} & {\bf 9.10} & {\bf 9.13} & \multirow{2}*{--} 
& {\bf 15.00} & {\bf 15.12} & \multirow{2}*{--} & {\bf 15.06} & 
{\bf + 0.06} \\ 
(C$_{40}$H$_{16}$) & & & & triplet & 9.76 & 9.82 & & 15.66 & 15.95 & 
& 15.75 & + 0.20 \\
\hline
Quaterrylene &  
\multirow{2}*{5.62} & \multirow{2}*{5.68} & 
\multirow{2}*{6.11~$\pm$~0.02} & {\bf singlet} & {\bf 8.50} & {\bf 8.55} & 
\multirow{2}*{--} & {\bf 14.12} & {\bf 14.35} & \multirow{2}*{--} & 
{\bf 14.23} & {\bf + 0.12}\\ 
(C$_{40}$H$_{20}$) & & & & triplet & 9.36 & 9.40 & & 14.97 & 15.08 & & 15.08 
& 0.00\\
\hline
Circumpyrene &  \multirow{2}*{6.06} & \multirow{2}*{6.10} & 
\multirow{2}*{--} & {\bf singlet} & {\bf 9.13} & {\bf 9.16} & 
\multirow{2}*{--} & {\bf 15.19} & {\bf 15.35} & \multirow{2}*{--} & 
{\bf 15.27} &  {\bf + 0.08} \\ 
(C$_{42}$H$_{16}$) & & & & triplet & 9.68 & 9.73 & & 15.75 & 15.80 & & 15.84 & 
$-$0.04\\
\hline
Hexabenzocoronene &  
\multirow{2}*{6.55} & \multirow{2}*{6.79} & \multirow{2}*{--} & 
singlet & 9.58 & 9.63 & \multirow{2}*{--} & 16.14 & 16.33 & 
\multirow{2}*{--} & 16.42 & $-$0.09 \\ 
(C$_{42}$H$_{18}$) & & & & {\bf triplet} & {\bf 9.52} & {\bf 9.57} & 
& {\bf 16.07} & {\bf 16.15} & & {\bf 16.36} & {\bf $-$0.21} \\
\hline
Dicoronylene &  
\multirow{2}*{6.07} & \multirow{2}*{6.13} & 
\multirow{2}*{--} & {\bf singlet} & {\bf 8.84} & {\bf 8.89} & 
\multirow{2}*{--} & {\bf 14.91} & {\bf 15.13} & 
\multirow{2}*{--} & {\bf 15.02} & {\bf + 0.11} \\ 
(C$_{48}$H$_{20}$) & & & & triplet & 9.37 & 9.40 & & 15.44 & 15.50 & 
& 15.53 & $-$0.03 \\
\hline
Pentarylene &  
\multirow{2}*{5.37} & \multirow{2}*{5.43} & 
\multirow{2}*{--} & {\bf singlet} & {\bf 7.92} & {\bf 7.97} & 
\multirow{2}*{--} & {\bf 13.29} & {\bf 13.51} & 
\multirow{2}*{--} & {\bf 13.39} & {\bf + 0.11}\\ 
(C$_{50}$H$_{24}$) & & & & triplet & 8.64 & 8.68 & & 14.00 & 14.10 & &
14.11 & $-${} 0.01\\
\hline
Circumcoronene &  \multirow{2}*{6.14} & \multirow{2}*{6.35} & 
\multirow{2}*{--} & {singlet} & 8.90 & 9.04 & 
\multirow{2}*{--} & 15.05 & 15.19 & 
\multirow{2}*{--} & 15.28 & $-$0.09\\ 
(C$_{54}$H$_{18}$) & & & & {\bf triplet} & {\bf 8.81} & {\bf 8.85} & & 
{\bf 14.95} & {\bf 15.00} & & {\bf 15.19} & {\bf $-$0.19}\\
\hline
Circumovalene &  
\multirow{2}*{5.71} & \multirow{2}*{5.74} & \multirow{2}*{--} & 
{\bf singlet} & {\bf 8.32} & {\bf 8.34} & \multirow{2}*{--} & 
{\bf 14.02} & {\bf 14.12} & \multirow{2}*{--} & 14.07 & +0.05 \\ 
(C$_{66}$H$_{20}$) & & & & triplet & 8.67 & 8.70 & & 14.37 & 14.42 & & 14.44 &
$-${} 0.02\\
\hline
\end{tabular}
\end{table}