TRANSIENT ABSORPTION CHANGES OF A DEGENERATE DIMER INDUCED BY EXCITONSCATTERING - IMPLICATIONS FOR PHOTOSYSTEM-II OF PHOTOSYNTHESIS

The effect of exciton scattering on transient absorption spectra of a degenerate dimer has been calculated from a simple four-level model. T he absorbance changes due to this scattering process not only depend o n the polarization of the probe beam, but also on the selectivity of e xcitation of specific exciton components. In the case of selective exc itation, the absorbance changes induced by exciton scattering may play an important role in time-resolved spectroscopy of the reaction cente r of Photosystem II at short times after excitation.