**Table 3:** Wavenumbers (in cm^-1) of the photoproducts that appeared after UV irradiation of pyridine, pyrimidine or s-triazine. The band assignments were taken from a Milligan & Jacox (1973); b Ruiterkamp et al. (2005); c Satoshi et al. (1997); and d Stroh & Winnewisser (1989). The bands for HCN and C₂H₂ in the pyrimidine photoproducts are shifted with respect to the bands given in the references, so a complex between HCN and C₂H₂ is inferred (see text).
$\begin{displaymath}\begin{tabular}{lr@{.}ll} \hline\hline Irradiation & \multi... ...d$ \\ & 904&1 & [HAr$_2$]$^+$ $^a$ \\ \hline \end{tabular}\end{displaymath}$