Institute of Experimental Physics, University of Gdańsk, 80-952, Gdańsk, Wita Stwosza 57, Poland.
J Fluoresc. 1995 Dec;5(4):307-19. doi: 10.1007/BF01152557.
High-accuracy Monte Carlo simulations of the time-dependent excitation probabilityG (s) (t) and steady-state emission anisotropyr M /r 0M for one-component three-dimensional systems were performed. It was found that the values ofr M /r 0M obtained for the averaged orientation factor[Formula: see text] only slightly overrate those obtained for the real values of the orientation factor κ ik (2) . This result is essentially different from that previously reported. Simulation results were compared with the probability coursesG (s) (t) andR(t) obtained within the frameworks of diagrammatic and two-particle Huber models, respectively. The results turned out to be in good agreement withR(t) but deviated visibly fromG (s) (t) at long times and/or high concentrations. Emission anisotropy measurements on glycerolic solutions of Na-fluorescein and rhodamine 6G were carried out at different excitation wavelengths. Very good agreement between the experimental data and the theory was found, with λex≈λ0-0 for concentrations not exceeding 3.5·10(-2) and 7.5·10(-3) M in the case of Na-fluorescein and rhodamine 6G, respectively. Up to these concentrations, the solutions investigated can be treated as one-component systems. The discrepancies observed at higher concentrations are caused by the presence of dimers. It was found that forλ ex <λ0-0 (Stokes excitation) the experimental emission anisotropies are lower than predicted by the theory. However, upon anti-Stokes excitation (λex>λ0-0), they lie higher than the respective theoretical values. Such a dispersive character of the energy migration can be explained qualitatively by the presence of fluorescent centers with 0-0 transitions differing from the "mean" at λ0-0.
对一维、三维各向同性和各向异性体系的时间依赖激发态布居概率 G(s)(t)和稳态发射各向异性 r M/r 0M 进行了高精度的蒙特卡罗模拟。结果表明，平均取向因子[Formula: see text]得到的 r M/r 0M 值仅略微高估了真实取向因子 κ ik(2)的相应值。这一结果与先前的报道有本质区别。模拟结果与图式和双粒子 Huber 模型框架下分别得到的概率曲线 G(s)(t)和 R(t)进行了比较。结果表明，R(t)与模拟结果吻合较好，但在长时间和/或高浓度下，G(s)(t)与模拟结果明显偏离。在不同的激发波长下，对 Na-荧光素和罗丹明 6G 的甘油溶液进行了发射各向异性测量。实验数据与理论结果非常吻合，在 Na-荧光素和罗丹明 6G 的浓度不超过 3.5·10(-2)和 7.5·10(-3) M 时，实验值与理论值符合得很好。在这些浓度下，所研究的溶液可以被视为单一组分体系。在更高的浓度下观察到的差异是由二聚体的存在引起的。结果表明，对于λ ex<λ0-0（Stokes 激发），实验发射各向异性低于理论预测。然而，在反斯托克斯激发（λ ex>λ0-0）时，它们高于相应的理论值。这种能量迁移的弥散特性可以通过存在与“平均”在 λ0-0 处不同的 0-0 跃迁的荧光中心来定性地解释。
