The study of the state [P870⁺ B800⁻] in bacterial reaction centers by selective picosecond and low‐temperature spectroscopies

Abstract

The selective picosecond excitation of Rhodopseudomonas sphaeroides (R‐26) reaction centers (RCs) at 870 nm induces the formation of the transient state within <1 ps followed by the conversion into the state P F (P ± Bph ±− during 7 ± 2 ps at both 293 K and 110 K. The transient state including the intense bleaching at 800 nm has been shown not to be due: (a) to photon excitation at 870 nm; (b) the excitation of P + ; (c) photoselection effects. The transient state is interpreted as the state 1 [P + B − ] in agreement with earlier works. The primary formation of the state 1 P + B − ] and the big effective singlet‐triplet splitting in this state correspond to the spectral splitting of the P band at 900 nm in R‐26 RCs and at 1000 nm in Rhodopseudomonas viridis RCs found at 4.2 K and attributed to the optical transition to both 1 P and 1 [P + B − ] states.