Automatic Feynman diagram generation for nonlinear optical spectroscopies and application to fifth-order spectroscopy with pulse overlaps.
Automatic Feynman diagram generation for nonlinear optical spectroscopies and application to fifth-order spectroscopy with pulse overlaps.
复制标题
用于非线性光学光谱的自动费曼图生成以及脉冲重叠五阶光谱的应用。
作者：
P. A. Rose;J. Krich
微扰非线性光谱是了解激子和其他凝聚相系统动力学的有力方法。费曼图长期以来一直是理解和解释实验光谱以及组织模型系统光谱计算的重要工具。当光脉冲严格按时间顺序排列时，只有少量的图有贡献，但在许多实验中，脉冲重叠效应对解释结果很重要。当脉冲重叠时，贡献图的数量可能会迅速增加，特别是在高阶光谱学中，并且当试图写下所有图时，人为错误尤其可能。我们提出了一个自动化的图形生成器（DG），生成计算任何n阶光谱信号所需的所有费曼图。我们的特点是所有微扰非线性光谱的相鉴别条件，以及脉冲幅度为非零的时间间隔。虽然DG可用于自动化脉冲计算，但其最大优势在于自动化脉冲重叠很重要的有限脉冲计算。我们考虑三阶瞬态吸收光谱和五阶激子-激子相互作用2D（EEI 2D）光谱，它们分别由六个或七个图描述，但当脉冲重叠时，分别由16个或240个图描述。DG允许用户以相对较低的计算成本自动包括所有相关图，因为额外的图仅针对它们相关的脉冲间延迟生成。对于EEI 2D光谱，我们显示了包括重叠图的重要影响。
Perturbative nonlinear optical spectroscopies are powerful methods to understand the dynamics of excitonic and other condensed phase systems. Feynman diagrams have long provided the essential tool to understand and interpret experimental spectra and to organize the calculation of spectra for model systems. When optical pulses are strictly time ordered, only a small number of diagrams contribute, but in many experiments, pulse-overlap effects are important for interpreting results. When pulses overlap, the number of contributing diagrams can increase rapidly, especially with higher order spectroscopies, and human error is especially likely when attempting to write down all the diagrams. We present an automated Diagram Generator (DG) that generates all the Feynman diagrams needed to calculate any nth-order spectroscopic signal. We characterize all perturbative nonlinear spectroscopies by their associated phase-discrimination condition as well as the time intervals where pulse amplitudes are nonzero. Although the DG can be used to automate impulsive calculations, its greatest strength lies in automating finite pulse calculations where pulse overlaps are important. We consider third-order transient absorption spectroscopy and fifth-order exciton-exciton interaction 2D (EEI2D) spectroscopy, which are described by six or seven diagrams in the impulsive limit, respectively, but 16 or 240 diagrams, respectively, when pulses overlap. The DG allows users to automatically include all relevant diagrams at a relatively low computational cost, since the extra diagrams are only generated for the inter-pulse delays where they are relevant. For EEI2D spectroscopy, we show the important effects of including the overlap diagrams.