ULTRAFAST DYNAMICS WITHIN THE B820 SUBUNIT FROM THE CORE (LH-1) ANTENNA COMPLEX OF RS-RUBRUM

Femtosecond transient dynamics within the dimeric subunit of a bacteri al light-harvesting complex have been investigated using magic angle a nd polarized pump-probe spectroscopy, Oscillations of 170 cm(-1) and a pproximate to 20 cm(-1), 50 cm(-1) and 115 cm(-1) are observed in the isotropic signal. and of approximate to 500 cm(-1) in the anisotropy; the Stokes shift and dephasing of the dimer exciton levels occurs on a sub-50 fs timescale, The re-assembled aggregate exhibits ultrafast sp ectral evolution and biphasic anisotropy decay. Collectively, the resu lts support a view of energy migration within LH-1 complexes as procee ding by strongly scattered excitation transfer between states of the d imeric subunits.