Ab initio computation of two-dimensional electronic spectra is an expanding field, whose goal is improving upon simple, few-dimensional models often employed to explain experiments. Here, we propose an accurate and computationally affordable approach, based on the single-trajectory semiclassical thawed Gaussian approximation, to evaluate two-dimensional electronic spectra. Importantly, the method is exact for arbitrary harmonic potentials with mode displacement, changes in the mode frequencies, and inter-mode coupling (Duschinsky effect), but can also account partially for the anharmonicity of the involved potential energy surfaces. We test its accuracy on a set of model Morse potentials and use it to study anharmonicity and Duschinsky effects on the linear and two-dimensional electronic spectra of phenol. We find that in this molecule, the anharmonicity effects are weak, whereas the Duschinsky rotation and the changes in the mode frequencies must be included in accurate simulations. In contrast, the widely used displaced harmonic oscillator model captures only the basic physics of the problem but fails to reproduce the correct vibronic lineshape.

中文翻译：

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二维电子光谱法对三阶响应函数的动态蝇头初始分类学评估

从头算二维电子光谱的计算是一个不断扩展的领域，其目标是改善通常用于解释实验的简单，少维度的模型。在这里，我们提出了一种基于单轨迹半经典解冻高斯近似的准确且计算上可以承受的方法，以评估二维电子光谱。重要的是，该方法适用于具有模式位移，模式频率变化和模式间耦合（Duschinsky效应）的任意谐波电势，但也可以部分解决所涉及的势能面的非谐性。我们在一组模型莫尔斯电势上测试其准确性，并用其研究苯酚的线性和二维电子光谱的不谐和杜尚斯基效应。我们发现在这个分子中 非谐性影响很弱，而精确模拟必须包括Duschinsky旋转和模式频率的变化。相反，广泛使用的位移谐波振荡器模型仅捕获了问题的基本物理原理，但无法再现正确的振动线形。