Moscow Pedagogical State University, 119435 Moscow, Russia.
J Chem Phys. 2011 Sep 28;135(12):125103. doi: 10.1063/1.3640891.
A theoretical six-level model for blinking fluorescence of single PPV-PPyV copolymer molecule excited by CW-laser light is proposed. The model has been chosen in accordance with the following facts found in the Paul Barbara group experiment: (i) alternation of two types of fluorescence with moderate and strong levels of emission, (ii) existence of "dark" states with no fluorescence, (iii) linear dependence of inverse on-interval duration on laser intensity, and (iv) existence of laser intensity independent off-intervals. Relations between the distribution function w''(N, T) for photons emitted by a single molecule, the distribution function w'(N, T) for photons arriving at photomultiplier tube (PMT) and photo-electric pulse distribution w(N, T) created in a PMT are discussed. The theory is able to describe pulse distribution function w(N, T) measured experimentally at signal acquisition time T = 0.1 s. Values of all rate constants of the model have been found from comparison of the theory with the experiment. Distributions w(on, off)(t) of on- and off-times and distribution w(N, T) of pulses have been calculated for infrequent and frequent inter-conformational jumps in single copolymer molecule.
提出了一个理论上的六级模型，用于研究单聚对苯乙炔-聚吡咯烷酮（PPV-PPyV）共聚物分子在连续激光激发下的闪烁荧光。该模型的选择是基于 Paul Barbara 小组实验中的以下事实：（i）两种发射强度中等和较强的荧光交替出现，（ii）存在无荧光的“暗态”，（iii）反脉冲间隔与激光强度呈线性关系，以及（iv）存在与激光强度无关的关断间隔。讨论了单分子发射的光子分布函数 w''(N, T)、到达光电倍增管（PMT）的光子分布函数 w'(N, T)和 PMT 中产生的光电脉冲分布函数 w(N, T)之间的关系。该理论能够描述在信号采集时间 T = 0.1 s 下实验测量的脉冲分布函数 w(N, T)。通过将理论与实验进行比较，找到了模型中所有速率常数的值。对于单共聚物分子中不频繁和频繁的构象跃迁，计算了 ON 和 OFF 时间分布 w(on, off)(t)和脉冲分布 w(N, T)。
