As noted above, the MS-CASPT2/SA-CASSCF method also allowed Oliveira et al. to identify a more efficient intersystem crossing channel with higher SOC between the S 1 and T 2 states. Overall, the PE profiles presented in this work are complementary to the photorelaxation mechanisms proposed by Oliveira et al. In particular, we were not able to locate the planar C6-puckered minimum of 9H 2,6-dAP and the more efficient S 1 /T 2 intersystem crossing of 7H 2,6-dAP. However, we identified C2-puckered S 1 minima and the associated photorelaxation mechanisms for both tautomers, located the S 1 /S 0 state crossing associated with the puckering of the 5-membered subunit of the purine aromatic ring of 7H 2,6-dAP and demonstrated the feasibility of the ballistic C6-puckering photorelaxation mechanism of 9H 2,6-dAP.