Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom.
Linacre College, University of Oxford, Oxford OX1 3JA, United Kingdom.
J Phys Chem A. 2023 Apr 27;127(16):3714-3727. doi: 10.1021/acs.jpca.3c00988. Epub 2023 Apr 13.
We present a dynamical simulation scheme to model the highly correlated excited state dynamics of linear polyenes. We apply it to investigate the internal conversion processes of carotenoids following their photoexcitation. We use the extended Hubbard-Peierls model, , to describe the π-electronic system coupled to nuclear degrees of freedom. This is supplemented by a Hamiltonian, , that explicitly breaks both the particle-hole and two-fold rotation symmetries of idealized carotenoid structures. The electronic degrees of freedom are treated quantum mechanically by solving the time-dependent Schrödinger equation using the adaptive time-dependent DMRG (tDMRG) method, while nuclear dynamics are treated via the Ehrenfest equations of motion. By defining adiabatic excited states as the eigenstates of the full Hamiltonian, , and diabatic excited states as eigenstates of , we present a computational framework to monitor the internal conversion process from the initial photoexcited 1B state to the singlet triplet-pair states of carotenoids. We further incorporate Lanczos-DMRG to the tDMRG-Ehrenfest method to calculate transient absorption spectra from the evolving photoexcited state. We describe in detail the accuracy and convergence criteria for DMRG, and show that this method accurately describes the dynamical processes of carotenoid excited states. We also discuss the effect of the symmetry-breaking term, , on the internal conversion process, and show that its effect on the extent of internal conversion can be described by a Landau-Zener-type transition. This methodological paper is a companion to our more explanatory discussion of carotenoid excited state dynamics in Manawadu, D.; Georges, T. N.; Barford, W. Photoexcited State Dynamics and Singlet Fission in Carotenoids. , , 1342.
我们提出了一种动力学模拟方案，用于模拟线性聚烯的高度相关激发态动力学。我们将其应用于研究类胡萝卜素在光激发后发生的内转换过程。我们使用扩展的 Hubbard-Peierls 模型 来描述与核自由度耦合的π电子系统。该模型通过一个哈密顿量 来补充，该哈密顿量明确打破了理想化类胡萝卜素结构的粒子-空穴和两倍旋转对称性。电子自由度通过使用自适应时间相关密度矩阵重整化群（tDMRG）方法求解含时薛定谔方程来进行量子力学处理，而核动力学则通过 Ehrenfest 运动方程来处理。通过将绝热激发态定义为全哈密顿量 的本征态，以及将非绝热激发态定义为 的本征态，我们提出了一个计算框架来监测内转换过程，该过程从初始光激发的 1B 态到类胡萝卜素的单重态三重态对态。我们进一步将 Lanczos-DMRG 纳入 tDMRG-Ehrenfest 方法，以从演化的光激发态计算瞬态吸收光谱。我们详细描述了 DMRG 的精度和收敛标准，并表明该方法可以准确描述类胡萝卜素激发态的动力学过程。我们还讨论了对称破缺项 对内部转换过程的影响，并表明它对内转换程度的影响可以用 Landau-Zener 型跃迁来描述。本文是我们对 Manawadu、D.；Georges，T. N.；Barford，W. 在《类胡萝卜素激发态动力学和 Singlet Fission 中的应用》一文中讨论类胡萝卜素激发态动力学的更具解释性的讨论的补充。
