University of Belgrade, Faculty of Physical Chemistry, Belgrade, Serbia.
Department of Physical Chemistry, Ruđer Bošković Institute, Zagreb, Croatia.
Phys Chem Chem Phys. 2021 Feb 4;23(4):2594-2604. doi: 10.1039/d0cp05618a.
Despite many studies, the mechanisms of nonradiative relaxation of uracil in the gas phase and in aqueous solution are still not fully resolved. Here we combine theoretical UV absorption spectroscopy with nonadiabatic dynamics simulations to identify the photophysical mechanisms that can give rise to experimentally observed decay time constants. We first compute and theoretically assign the electronic spectra of uracil using the second-order algebraic-diagrammatic-construction (ADC(2)) method. The obtained electronic states, their energy differences and state-specific solvation effects are the prerequisites for understanding the photodynamics. We then use nonadiabatic trajectory-surface-hopping dynamics simulations to investigate the photoinduced dynamics of uracil and uracil-water clusters. In contrast to previous studies, we found that a single mechanism - the ethylenic twist around the C[double bond, length as m-dash]C bond - is responsible for the ultrafast component of the nonradiative decay, both in the gas phase and in solution. Very good agreement with the experimentally determined ultrashort decay time constants is obtained.
尽管进行了许多研究，但尿嘧啶在气相和水溶液中非辐射弛豫的机制仍未完全解决。在这里，我们将理论紫外吸收光谱与非绝热动力学模拟相结合，以确定可能导致实验观察到的衰减时间常数的光物理机制。我们首先使用二阶代数图式构造（ADC(2)）方法计算并理论分配尿嘧啶的电子光谱。获得的电子态、它们的能量差异和态特异性溶剂化效应是理解光动力学的前提。然后，我们使用非绝热轨迹表面跳跃动力学模拟来研究尿嘧啶和尿嘧啶-水团簇的光诱导动力学。与以前的研究相比，我们发现，无论是在气相还是在溶液中，单一致变机制 - 即 C[双键，长度为破折号]C 键周围的双键扭曲 - 负责非辐射衰减的超快成分。与实验确定的超短衰减时间常数非常吻合。
