We have applied the model of extended states to the ring antenna syste
m LH2 of Rps. acidophila, In the framework of the Generalized Master E
quations method, we investigate the memory functions and the exciton c
oherence time, taking into account the interaction of the exciton with
the static and dynamic disorders. The stochastic Liouville equations
are used to model the transfer of the exciton between neighboring ring
s.