Characterizing the functional dynamics of zinc phthalocyanine from femtoseconds to nanoseconds

A promising photosensitizer, zinc phthalocyanine, is investigated by means of steady-state and time-resolved pump-probe spectroscopies. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds. Global analysis yields the excited-state absorption spectra and lifetimes, as well as the pathways and efficiencies of the competing relaxation processes from the initially excited S1 state. In addition to the expected nanosecond-scale processes of fluorescence, internal conversion and inter-system crossing that follow the generally accepted kinetic scheme, we also resolve ultrafast dynamics. The nature of these fast processes and their implications to the functional pathway involving triplet formation are discussed.