Nonperturbative theory of femtosecond time-resolved spectroscopy: optical N-wave mixing and strong-pulse spectroscopies

本研究项目旨在进一步发展多原子分子的多脉冲UV/Vis激光光谱理论。与基于微扰非线性光学理论的主流方法不同，我们详细阐述了飞秒时间分辨光谱的非微扰描述。在弱场条件下，当非微扰理论应用于复杂材料系统时，其计算效率高于传统方法。在强场区域，除了非微扰描述之外，没有其他选择。我们将研究二维UV/Vis光谱和偏振敏感泵浦-探测光谱(四波混频光谱的两个例子)在探测电子势能面锥形交叉处的超快动力学方面的潜力。我们将对两种新型的六波混频光谱(飞秒受激拉曼光谱和外差三维光学光谱)的信号进行计算模拟。我们将对飞秒双泵浦单分子光谱这一新颖而非常有前途的技术进行理论描述，并考虑其应用。我们将探索强场现象，如电子Rabi循环，在多大程度上可以为复杂分子系统的超快非绝热动力学提供新的光谱信息。

This research project aims at the further development of the theory of multiple-pulse UV/vis laser spectroscopy of polyatomic molecules. Deviating from the main-stream approach, which is based on the formalism of perturbative nonlinear optics, we elaborate a nonperturbative description of femtosecond time-resolved spectroscopy. In the weak-field regime, the nonperturbative theory is computationally more efficient than the traditional approach when applied to complex material systems. In the strong-field regime, there is no alternative to a nonperturbative description. We will investigate the potential of two-dimensional UV/vis spectroscopy and of polarization-sensitive pump-probe spectroscopy (two examples of four-wave-mixing spectroscopies) for the detection of ultrafast dynamics at conical intersections of electronic potential-energy surfaces. We will perform computational simulations of the signals of two novel six-wave-mixing spectroscopies (femtosecond stimulated Raman spectroscopy and heterodyned three-dimensional optical spectroscopy). We will develop a theoretical description of the novel and very promising technique of femtosecond double-pump single-molecule spectroscopy and will consider applications. We will explore to which extent strong-field phenomena, such as electronic Rabi cycling, can provide novel spectroscopic information on the ultrafast nonadiabatic dynamics of complex molecular systems.