基于耦合簇理论非绝热动力学模拟的吡嗪光谱光弛豫特征
Spectroscopic photorelaxation signatures in pyrazine from nonadiabatic dynamics simulations with coupled cluster theory
AI总结：
研究吡嗪光激发后超快弛豫机制，用耦合簇理论等方法模拟其超快激发态动力学，与实验光电子能谱和X射线吸收光谱对比，提供对光弛豫中态相互作用的深入见解。
摘要：
尽管有大量理论和实验工作，但光激发后吡嗪超快弛豫的机制仍难以厘清。近期理论研究趋向三态机制。本文用耦合簇理论等对吡嗪超快激发态动力学进行高级模拟，给出时间分辨光电子能谱等预测，与实验有定量和定性相符，还详述了光谱特征。
英文摘要：
Despite extensive theoretical and experimental efforts, the mechanisms underlying the ultrafast relaxation of pyrazine after photoexcitation remain challenging to disentangle. Recently, theoretical investigations have been converging towards a three-state mechanism, with an ultrafast decay of the bright ${}^{1}B_{2u}$ state followed by beats in the populations of the low-lying ${}^{1}B_{3u}$ and ${}^{1}A_u$ states. However, a clear agreement between the experimental results and the corresponding theoretical predictions remains elusive. Here, we present a high-level simulation of the ultrafast excited states dynamics of pyrazine using coupled cluster theory with single and double excitations and ab initio multiple spawning, together with predictions of the time-resolved photoelectron spectrum and X-ray absorption spectra at the nitrogen and carbon edges. This is made possible by using a newly developed multistate implementation of similarity constrained coupled cluster theory. We find quantitative agreement with the experimental signature of the ${}^{1}B_{2u}$ decay in the photoelectron spectrum, and qualitative agreement with the available experimental X-ray absorption spectra. Moreover, we detail spectroscopic signatures that should be verifiable in experiments with sufficient resolution in the time and frequency domains. Compared to previous theoretical studies, we provide further detailed insight into the interplay of the states involved in the photorelaxation.
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