Seliya Pankaj, Bonn Mischa, Grechko Maksim
Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
J Phys Chem Lett. 2023 Sep 28;14(38):8630-8637. doi: 10.1021/acs.jpclett.3c01974. Epub 2023 Sep 20.
The interaction of quantum-mechanical systems with a fluctuating thermal environment (bath) is fundamental to molecular mechanics and energy transport/dissipation. Its complete picture requires mode-specific measurements of this interaction and an understanding of its nature. Here, we present a combined experimental and theoretical study providing detailed insights into the coupling between a high-frequency vibrational two-level system and thermally excited terahertz modes. Experimentally, two-dimensional terahertz-infrared-visible spectroscopy reports directly on the coupling between quantum oscillators represented by CH streching vibrations in liquid dimethyl sulfoxide and distinct low-frequency modes. Theoretically, we present a mixed quantum-classical formalism of the sample response to enable the simultaneous quantum description of high-frequency oscillators and a classical description of the bath. We derive the strength and nature of interaction and find different coupling between CH stretch and low-frequency modes. This general approach enables quantitative and mode-specific analysis of coupled quantum and classical dynamics in complex chemical systems.
量子力学系统与波动的热环境（热库）之间的相互作用是分子力学以及能量传输/耗散的基础。要全面了解这一相互作用，需要对其进行特定模式的测量，并深入理解其本质。在此，我们开展了一项结合实验与理论的研究，对高频振动二能级系统与热激发太赫兹模式之间的耦合进行了详细深入的探讨。在实验方面，二维太赫兹-红外-可见光光谱直接揭示了以液态二甲亚砜中碳氢键伸缩振动所代表的量子振子与不同低频模式之间的耦合。在理论方面，我们提出了一种样本响应的混合量子-经典形式体系，以便能够同时对高频振子进行量子描述，以及对热库进行经典描述。我们推导出了相互作用的强度和本质，发现碳氢键伸缩振动与低频模式之间存在不同的耦合。这种通用方法能够对复杂化学系统中耦合的量子和经典动力学进行定量且特定模式的分析。
