Non-conservative circular dichroism of photosystem II reaction centers: Is there an enhancement by a coupling with charge transfer states?
Sprache des Vortragstitels:
Quantum Dynamics and Spectroscopy of Functional Molecular Materials and Biological Photosystems
Sprache des Tagungstitel:
The non-conservative nature of the circular dichroism (CD) spectrum of the Qy spectral region of the D1/D2/cytb559 reaction center complexes of photosystem II ist investigated. Our theory, in addition to the usual excitonic couplings between the low-energy Qy transitions of the chlorophyll and pheophytin pigments, takes into account the coupling of the Qy with the higher-engery Bx, By and Nx+xy transitions of these pigments and with S0-S2 transitions of the two ß-carotene pigments in the complex. The higher-engery transitions are parameterized by using quantum chemical calculations and an analysis of the experimental oscillator strength of the isolated pigments. The Poisson-TrEsp method is used to obtain the excitonic coulings between pigments, whereas the coupling between exciton and charge transfer states in the central PD1-PD2 pigments is implicitly taken into account by a scaling factor of the obtained excitonic coupling of the dimer. It is shown that the observed non-conservativity of the Qy CD spectrum can be qualitatively understood by the above described mixing of Qy and higher-energy transitions and the analysis further suggests, that the non-conservativity may be enhanced by coupling to charge transfer states.