Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina.
Centre for Quantum Materials and Technologies, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom.
J Chem Phys. 2023 Apr 14;158(14):144104. doi: 10.1063/5.0142094.
Real time modeling of fluorescence with vibronic resolution entails the representation of the light-matter interaction coupled to a quantum-mechanical description of the phonons and is therefore a challenging problem. In this work, taking advantage of the difference in timescales characterizing internal conversion and radiative relaxation-which allows us to decouple these two phenomena by sequentially modeling one after the other-we simulate the electron dynamics of fluorescence through a master equation derived from the Redfield formalism. Moreover, we explore the use of a recent semiclassical dissipative equation of motion [C. M. Bustamante et al., Phys. Rev. Lett. 126, 087401 (2021)], termed coherent electron electric-field dynamics (CEED), to describe the radiative stage. By comparing the results with those from the full quantum-electrodynamics treatment, we find that the semiclassical model does not reproduce the right amplitudes in the emission spectra when the radiative process involves the de-excitation to a manifold of closely lying states. We argue that this flaw is inherent to any mean-field approach and is the case with CEED. This effect is critical for the study of light-matter interaction, and this work is, to our knowledge, the first one to report this problem. We note that CEED reproduces the correct frequencies in agreement with quantum electrodynamics. This is a major asset of the semiclassical model, since the emission peak positions will be predicted correctly without any prior assumption about the nature of the molecular Hamiltonian. This is not so for the quantum electrodynamics approach, where access to the spectral information relies on knowledge of the Hamiltonian eigenvalues.
具有振子分辨率的荧光实时建模需要将光与物质的相互作用表示为与声子的量子力学描述耦合，因此这是一个具有挑战性的问题。在这项工作中，我们利用内部转换和辐射弛豫的特征时间尺度的差异——这允许我们通过依次逐个模拟这两个现象来解耦这两个现象——通过从 Redfield 形式主义推导出的主方程来模拟荧光的电子动力学。此外，我们探索了使用最近的半经典耗散运动方程 [C. M. Bustamante 等人，Phys. Rev. Lett. 126, 087401 (2021)]，称为相干电子电场动力学（CEED），来描述辐射阶段。通过将结果与全量子电动力学处理的结果进行比较，我们发现当辐射过程涉及到一组紧密排列的状态时，半经典模型不会在发射光谱中再现正确的幅度。我们认为这种缺陷是任何平均场方法所固有的，CEED 也是如此。这种效应对于光与物质相互作用的研究至关重要，据我们所知，这是首次报道这一问题的工作。我们注意到，CEED 以与量子电动力学一致的方式再现了正确的频率。这是半经典模型的一个主要优势，因为无需对分子哈密顿量的性质做出任何假设，就可以正确预测发射峰的位置。对于量子电动力学方法来说并非如此，在这种方法中，获得光谱信息依赖于对哈密顿量本征值的了解。
