The black-brown pigment eumelanin acts as a vital barrier to the harmful UV radiation. With an ingeniousability to effectively dissipate 99.9% of the incoming UV energy to the heat within few picoseconds, eumelaninserves as a natural photo-protectant. To unravel the nature of the energy dissipation we study the eumelaninpigment and its major building block using ultrafast broadband transient absorption spectroscopy. The excitedstate decay was found to be uence independent for all excitation energies, suggesting that electronic excitationsare also spatially localized. The short excited state lifetime - on the order of a few picoseconds - leads to asuggestion that the energy is dissipated through excited-state intramolecular proton transfer, which we examinedvia comparison with pH-dependent TA spectroscopy of the DHICA and related building blocks.
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