Novoderezhkin V I, Razjivin A P
Scientific Research Center on Technological Lasers, Russian Academy of Science, Troizk, Moscow Region.
Biophys J. 1995 Mar;68(3):1089-100. doi: 10.1016/S0006-3495(95)80283-3.
A theoretical model of exciton dynamics in circular molecular aggregates of light-harvesting bacteriochlorophyll of photosynthetic bacteria is proposed. The spectra and anisotropy of photoinduced absorption changes in the femto- and picosecond time domain are under its scope. The excited state of aggregate was treated due to the standard exciton theory, taking into account a pigment inhomogeneity. Dephasing processes via the exciton-phonon interactions were described by means of the Haken-Strobl equation. It was shown that only two exciton levels are dipole-allowed in the case of homogeneous circular aggregate. The pigment inhomogeneity results in the appearance of several weak transitions to higher exciton levels. It was proposed that the minor band (B896) in an absorption spectrum of the B875 complex as well as the similar minor band in spectra of B800-850 complex correspond to electron transition from the ground to the lowest exciton level, whereas the major band corresponds to transition to the higher exciton level. The proposed model shows the subpicosecond decay of anisotropy at the short-wavelength side of absorption band and a high degree of anisotropy at the long-wavelength side, even at high temperatures.
提出了光合细菌捕光细菌叶绿素圆形分子聚集体中激子动力学的理论模型。飞秒和皮秒时域内光致吸收变化的光谱和各向异性在其研究范围内。考虑到色素的不均匀性，根据标准激子理论处理聚集体的激发态。通过哈肯 - 施特罗布尔方程描述了激子 - 声子相互作用引起的退相过程。结果表明，在均匀圆形聚集体的情况下，只有两个激子能级是偶极允许的。色素的不均匀性导致出现几个向更高激子能级的弱跃迁。有人提出，B875复合物吸收光谱中的小带（B896）以及B800 - 850复合物光谱中的类似小带对应于从基态到最低激子能级的电子跃迁，而主带对应于到更高激子能级的跃迁。所提出的模型表明，即使在高温下，吸收带短波侧的各向异性在亚皮秒时间内衰减，而长波侧具有高度的各向异性。
