The non-conservative nature of the circular dichroism (CD) spectrum of the ${\text{Q}}_y$ spectral region of the D1/D2/Cytb₅₅₉ reaction center complexes of photosystem II is investigated. Our theory, in addition to the usual excitonic couplings between the ${\text{Q}}_y$ transitions of the chlorophyll and pheophytin pigments, takes into account the coupling of the ${\text{Q}}_y$ with the higher-energy ${\text{B}}_x$, ${\text{B}}_y$ and ${\text{N}}_{x+xy}$ transitions of these pigments and with ${\text{S}}_0\to {\text{S}}_2$ transitions of the two β-carotene pigments close to the reaction center. The higher-energy transitions are parameterized by quantum chemical calculations and an analysis of the experimental oscillator strength of the isolated pigments. The excitonic couplings between pigments are obtained with the Poisson-TrEsp method. The coupling between exciton and charge transfer states in the central P_D1-P_D2 dimer is implicitly taken into account by a scaling factor of the excitonic coupling. The observed non-conservativity of the ${\text{Q}}_y$ CD spectrum can be qualitatively understood by the above described mixing of ${\text{Q}}_y$ and higher-energy transitions. The analysis suggests that the non-conservativity may be enhanced by coupling to charge transfer states. We expect that the present study will stimulate explicit microscopic studies of the charge transfer states in the reaction center of photosystem II.

圆二色（CD）光谱的非保守性质。 ${\text{问}}_{ÿ}$研究了光系统II的D1 / D2 / Cyt b ₅₅₉反应中心配合物的光谱区域。我们的理论，除了通常的激子之间的耦合${\text{问}}_{ÿ}$ 叶绿素和脱镁叶绿素色素的过渡过程考虑了 ${\text{问}}_{ÿ}$ 能量更高 ${\text{乙}}_X$， ${\text{乙}}_{ÿ}$ 和 ${\text{ñ}}_{X+Xÿ}$ 这些颜料的过渡以及 ${\text{小号}}_0\to {\text{小号}}_2$靠近反应中心的两种β-胡萝卜素颜料的过渡 通过量子化学计算和对分离出的颜料的实验振荡器强度的分析来对较高能的跃迁进行参数化。颜料之间的激子偶合是通过Poisson-TrEsp方法获得的。在中心P激子和电荷转移的状态之间的耦合_D1 -P _D2二聚体是通过激子耦合的缩放因子隐式地考虑。观察到的非保守性${\text{问}}_{ÿ}$ 通过以上所述的CD混合可以定性地理解CD光谱 ${\text{问}}_{ÿ}$以及更高能量的过渡。分析表明，可以通过与电荷转移状态耦合来增强非保守性。我们希望本研究将激发光系统II反应中心中电荷转移状态的微观研究。