ИСТИНА

By making an assumption of rotation of two ortho/papa water molecules located nearby of the special pair in the reaction center of purple bacteria, the femtosecond transient absorption kinetics of the charge-separation states have been modeled. The mutual conversion of the ortho/para water molecule spin-isomers is a key feature which allows to drive the electron transfer process. The third order nonlinear response has been calculated including the stimulated emission and the excited-state absorption using the density matrix equations with the Redfield relaxation operator. The model allows us to obtain a quantitative fit of the experimental kinetics around 900 nm and 1050 nm range.