DYNAMICS OF FRENKEL EXCITONS IN DISORDERED MOLECULAR AGGREGATES
DYNAMICS OF FRENKEL EXCITONS IN DISORDERED MOLECULAR AGGREGATES
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DOI：
10.1063/1.460220
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发表时间：
1991-05-15
影响因子：
4.4
通讯作者：
WIERSMA, DA
中科院分区：
文献类型：
--
作者：
FIDDER, H;TERPSTRA, J;WIERSMA, DA
本文报道了假异氰酸-溴化物和碘化物聚集体的光学动力学。讨论了乙二醇/水玻璃中PIC-Br的共振光散射（RLS）、时间分辨发射和光子回波衰减的测量结果。基于线性链模型的带结构计算对J聚集体也进行了。结果表明，J带可以被描述为一个无序的弗伦克尔激子带，其中存在延伸约100个分子的超辐射态。基于对角位能不相关的Anderson’s hamilton对J波段的数值模拟研究表明，无序参数D与最近邻耦合参数J12的比值kappa约为0.11。利用振动荧光和拉曼散射产率之比的频率依赖性作为探针，研究了三种不同温度下的脱相过程和浴浴相关函数的推导参数。结果表明，在所有温度下激子消相过程都发生在快调制极限。对于Langmuir-Blodgett薄膜中的PIC-I，光激发也可以用能带跃迁来描述，但无序性比玻璃中的要大得多。该系统的低温荧光寿命约为10 ps，这表明激发远比玻璃中自组装聚集体的激发更离域。双能级PIC的共振瑞利散射实验表明，在重整带边缘以上的能量处，激子减相速率显著增加。
This article reports on the optical dynamics in aggregates of pseudoisocyanine-bromide and iodide. For PIC-Br in an ethylene glycol/water glass, the results of resonance light scattering (RLS), time-resolved emission, and photon echo decay measurements are discussed. Band structure calculations based on a linear-chain model for the J aggregate have also been performed. The results show that the J band can be described as a disordered Frenkel exciton band in which superradiant states exist that extend over about 100 molecules. Numerical simulation studies of the J band, based on Anderson's Hamiltonian with uncorrelated diagonal site energies, show that the ratio kappa of the disorder parameter D over the nearest-neighbor coupling parameter J12 is about 0.11. Using the frequency dependence of the ratio between the yields of vibrational fluorescence and Raman scattering as a probe, the dephasing process and derived parameters for the bath correlation function at three different temperatures have also been examined. It is shown that at all temperatures the exciton dephasing process occurs in the fast modulation limit. For PIC-I in a Langmuir-Blodgett film the optical excitation can be described also in terms of a band transition but the disorder is much larger than in a glass. For this system, a low-temperature fluorescence lifetime of about 10 ps is measured, which suggests that the excitation is much more delocalized than in the case of self-assembled aggregates in a glass. Resonance Rayleigh scattering experiments on PIC in a bilayer show that the exciton-dephasing rate increases dramatically at energies above the renormalized band edge.