Burning of a narrow spectral hole at 1.7 K in the absorbance band of the primary electron donor of Rhodopseudomonas viridis reaction centers with blocked electron transfer

Burning of spectral holes within the absorption band of the primary electron donor P in reaction centers of Rhodopseudomonas viridis is studied using selective excitation at 1014 nm and 1.7 K. A narrow (≤ 1.0 cm −1) spectral hole with relatively weak electron-phonon and vibronic coupling is burned if the intermediary electron acceptor I is pre-reduced. The hole is broadened up to ∼90–150 cm −1 if I is neutral and the electron-transfer chain is open. Broadening of the hole is discussed in terms of the fast (∼70–110 fs) electron hopping between P* and P +BL − (BL, bacteriochlorophyll monomer in L protein subunit).