Femtosecond pump-probe spectroscopy of bacteriochlorophyll a monomers in solution.

AUTOR(ES)

Savikhin, S

RESUMO

One- and two-color absorption difference profiles were obtained for BChl a in 1-propanol with approximately 50-fs resolution, using a self-mode-locked Ti:sapphire laser system. Time evolution in the BChl a absorption difference spectrum produces nonexponential photobleaching/stimulated emission (PB/SE) decay kinetics in 800-nm one-color experiments. Nonexponential PB/SE rise behavior occurs for some combinations of pump and probe wavelengths in two-color experiments. Optimized parameters from triexponential fits to the absorption difference profiles depend markedly on the fitting time window; they typically include a minor component with lifetime in the hundreds of fs. Much of the latter component is due to vibrational relaxation and/or intramolecular vibrational redistribution, rather than solvent dielectric relaxation. Measurements of the pump-probe anisotropy indicate that the electronic transition moment for the broad Qy excited state absorption band that overlaps the Qy steady-state absorption spectrum makes an angle of at most 20 degrees from that of the ground-->Qy state transition. No coherent oscillations are observed at early times. Our results bear directly on the interpretation of fs pump-probe experiments on BChl a-containing pigment-protein complexes.

Documentos Relacionados

• Fluorescence lifetime imaging by asynchronous pump-probe microscopy.
• Pump-probe anisotropies of Fenna-Matthews-Olson protein trimers from Chlorobium tepidum: a diagnostic for exciton localization?
• Femtosecond probe of structural analogies between chlorosomes and bacteriochlorophyll c aggregates.
• Na+ pump current-voltage relationships of rabbit cardiac Purkinje cells in Na(+)-free solution.
• Nitrogen electron nuclear double resonance and proton triple resonance experiments on the bacteriochlorophyll cation in solution.