Excited-state properties of biliproteins: I. phytochrome Pr

Phytochrome Pr has been investigated by means of picosecond intensity-depen dent transmission measurements at several excitation wavelengths inside the S-0 --> S-1 absorption band. The experimental data exhibit relatively stro ng excited-state absorption (ESA) within the whole spectral range of the S- 0 --> S-1 absorption, which is followed by fast relaxations on the femtosec ond time scale ( < 200 fs). The ESA cross sections at wavelengths below 640 nm are lower than those of the ground-state absorption, but they are notic eably larger at the maximum and at the long-wavelength side where stimulate d emission additionally influences the bleaching behaviour. The spectral ch aracteristics of the emission cross sections have been shown to be a good m easure for the comet radiative Lifetime ro. This confirmed our recently pub lished value of tau(0) = 4.9 ns. (C)1999 Elsevier Science S.A. All rights r eserved.