Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States.
J Phys Chem B. 2013 Dec 12;117(49):15272-84. doi: 10.1021/jp4057913. Epub 2013 Sep 9.
Multiple population-period transient spectroscopy (MUPPETS) is a six-pulse experiment with two time dimensions that is capable of adding information about systems with complicated kinetics. The core theory for MUPPETS focuses on the χ(5) response of the chromophores. This theory was used to analyze the dynamics of excitons and biexcitons in CdSe/ZnS core-shell nanoparticles in part I of this paper [J. Phys. Chem. B 2013, DOI:10.1021/jp405785a]. In real experiments, the potential role of additional processes must also be considered, in particular, the χ(7), "saturation" of the MUPPETS signal and nonresonant signals from heating of the solvent. A pathway method for calculating fluence effects in MUPPETS is developed. The fluence dependence of the biexciton signal and its sign reversal, as found in part I, are explained without invoking higher excitons or unexpected species. A method is presented for quantitatively predicting the magnitude of signals from solvent heating using an external standard. Thermal effects in this system are found to be too small to affect the conclusions in part I. Their small size, combined with small, systematic errors in the data, also makes it difficult to measure the yield of solvent heat in these experiments.
多组元-多脉冲瞬态光谱（MUPPETS）是一种具有两个时间维度的六脉冲实验，能够为动力学复杂的体系提供更多信息。MUPPETS 的核心理论侧重于发色团的 χ(5)响应。该理论用于分析 CdSe/ZnS 核壳纳米粒子中激子和双激子的动力学，这是本文第一部分的内容 [J. Phys. Chem. B 2013, DOI:10.1021/jp405785a]。在实际实验中，还必须考虑其他附加过程的潜在作用，特别是 χ(7)、MUPPETS 信号的“饱和”以及溶剂加热产生的非共振信号。本文提出了一种用于计算 MUPPETS 中光强效应的途径方法。第一部分发现的双激子信号的光强依赖性及其符号反转无需涉及更高的激子或意外的物质即可得到解释。提出了一种使用外部标准定量预测溶剂加热信号幅度的方法。发现该体系中的热效应太小，不会影响第一部分的结论。由于数据中存在小的系统误差和较小的热效应，也难以在这些实验中测量溶剂热的产率。
