Abstract

Although much work has focused, on the dynamics prior to and during charge separation in the photosynthetic reaction center,¹ many issues remain unresolved, including the nature of the upper excitonic state of the electronically excited special pair (P_y-1, where P is the special pair ground state) and its influence on energy and electron transfer.^2,3 In this report we present “two color" wavelength-resolved pump-probe anisotropy measurements⁴ of the photosynthetic reaction center (RC) of Rhodobacter Sphaeroides at room temperature, The major Q_y absorption bands arc collectively excited using short (13-18 fs) pulses with a broad spectral range, or individually excited with longer, spectrally narrowed pulses, which overlap with the trairsition (s) of interest. A broadband probe records the response of the system with respect to wavelength, time, and polarization. The resulting “two color” pump probe an isotropy transients yield detailed experimental descriptions of the dynamics prior to charge separation, particularly energy transfer from B to P.

© 1997 Optical Society of America