Photoselection effects in laser flash-induced spin-polarised EPR spectra of the radical pair state [P+QA−] in Rhodobacter sphaeroides reaction centers

The spin-polarised EPR signal of the radical pair state [P+QA−] in Zn-substituted Rhodobacter sphaeroides R26 reaction centers demonstrates a strong dependence on the wavelength and polarisation of the excitation light. This dependence is attributed to photoselection by the plane-polarised laser light utilised in the experiments. The model of spin-correlated radical pairs describes the experimental results well if the effect of photoselection is taken into account.