In addition to the photorelaxation pathways which match our experimental observations, we have identified two other radiationless deactivation mechanisms of 2,6-dAP, that fall outside of our experimentally observable parameters. Similarly to the 9H tautomer, UV-excited 7H 2,6-dAP could undergo ring-puckering of the six-membered subunit of the aromatic purine ring, involving pyramidalization of the C2 carbon atom (see Fig. ). According to our calculations, the associated S 1 minimum lies approximately 0.6 eV higher in energy than the origin transition (and the energy of our pump pulse) and is very unlikely to be populated in our experiments. Note that the geometry of this S 1 (ππ*) minimum is mainly associated with the puckering of the 6-membered aromatic subunit on the C2 atom, in contrast to the puckering of the 5-membered aromatic subunit in the case of the primary S 1 minimum of 7H 2,6-dAP discussed in the previous section. In addition, the corresponding S 1 (ππ*)/S 0 conical intersection is also higher in energy than the C 2 -puckered S 1 minimum and has a clearly sloped topography. Nevertheless, this alternative photorelaxation channel of the 7H tautomer could be triggered at higher excitation energies than those in our experiments.