Interconnection between Polarization-Detected and Population-Detected Signals: Theoretical Results and Ab Initio Simulations,Journal of Chemical Theory and Computation

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Interconnection between Polarization-Detected and Population-Detected Signals: Theoretical Results and Ab Initio Simulations
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2024-08-26 , DOI: 10.1021/acs.jctc.4c00592
Kewei Sun ₁ , Luis Vasquez ₁ , Raffaele Borrelli ₂ , Lipeng Chen ₃ , Yang Zhao ₄ , Maxim F Gelin ₁

Affiliation

Most of spectroscopic signals are specified by the nonlinear laser-induced polarization. In recent years, population-detection of signals becomes a trend in femtosecond spectroscopy. Polarization-detected (PD) and population-detected signals are fundamentally different, because they are determined by photoinduced processes acting on disparate time scales. In this work, we consider the fluorescence-detected (FD) N-wave-mixing (NWM) signal as a representative example of population-detected signals, derive a rigorous expression for this signal, and discuss its approximate variants suitable for numerical simulations. This leads us to the definition of the phenomenological FD (PFD) signal, which contains as a special case all definitions of FD signals available in the literature. Then we formulate and prove the population-polarization equivalence (PPE) theorem, which states that PFD NWM signals produced by (possibly strong) laser pulses can be evaluated as conventional PD signals in which the effective polarization is determined by the PFD transition dipole moment operator. We use the PPE theorem for the construction of the ab initio protocol for the simulation of PFD 4WM signals. As an example, we calculate electronic two-dimensional (2D) PFD spectra of the gas-phase pyrazine and compare them with the corresponding PD 2D spectra.

中文翻译：

偏振检测信号和群体检测信号之间的互连：理论结果和从头算仿真

大多数光谱信号是由非线性激光诱导偏振指定的。近年来，信号的群体检测成为飞秒光谱学的趋势。偏振检测（PD）信号和群体检测信号有着根本的不同，因为它们是由作用在不同时间尺度上的光诱导过程决定的。在这项工作中，我们将荧光检测（FD） N波混合（ N WM）信号视为群体检测信号的代表性示例，推导出该信号的严格表达式，并讨论其适合数值模拟的近似变体。这引出了现象学 FD (PFD) 信号的定义，其中包含文献中可用的 FD 信号的所有定义作为特例。然后，我们制定并证明了群体极化等效（PPE）定理，该定理指出，由（可能很强的）激光脉冲产生的 PFD N WM 信号可以被评估为传统的 PD 信号，其中有效极化由 PFD 跃迁偶极矩决定操作员。我们使用 PPE 定理构建从头算协议来模拟 PFD 4WM 信号。作为一个例子，我们计算了气相吡嗪的电子二维 (2D) PFD 光谱，并将其与相应的 PD 2D 光谱进行比较。

更新日期：2024-08-26

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