White-light continuum probed femtosecond time-resolved absorption spectroscopic measurement of β-carotene under high pressure

We have performed a femtosecond time-resolved absorption spectroscopic experiment of β-carotene in n-hexane solution under high pressure up to ∼1.0 GPa. Using white-light continuum in the visible spectral region as probe light, we found that the energy level of S ₁ state descends, whereas its lifetime becomes longer with the rising pressure. We ascribe this tendency deviating from the energy gap law to the viscosity effects on the CC stretching vibrations, which is fully consistent with the microviscosity theory. This Letter may provide some insights on the light harvesting and photoprotection functions of carotenoids in photosynthetic organisms.