On the other hand, excitation of Aza at 334 nm or 316 nm is proposed to result in the population of both the S2 and the S1 states, which the former decaying by ultrafast internal conversion to the S1 state (not shown in Scheme 3b). The S1 state primarily relaxes by intramolecular charge separation and charge recombination to the ground state within 1, while a minor fraction of the excited state population in the singlet manifold intersystem crosses to the triplet manifold leading to the population of the T1 state with a very small yield (from ca. 15 to 3% depending on pH). Even though there are quantitative differences in the rates governing the deactivation pathways of Aza depending on whether the neutral or the deprotonated form of Aza is investigated (or whether PBS or acetonitrile is used), the qualitative deactivation mechanism seems to be similar.