We first focus on elucidating the electronic relaxation mechanism for 6MP in aqueous solution at three different pHs. The evolution-associated difference spectra extracted from a global and target analysis of the transient absorption data reported in Figure satisfactorily captures all the observed spectral changes (see Figure ). Hence, a direct comparison of the evolution-associated difference spectra with the calculated excited-state absorption spectra for the S2(ππ*), S1(nπ*), T2(nπ*) and T1(ππ*) states, reported in Figure , is expected to provide crucial information about the excited states that participate in the relaxation mechanism.