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Exploring the capabilities of optical pump X-ray probe NEXAFS spectroscopy to track photo-induced dynamics mediated by conical intersections.
Faraday Discussions ( IF 3.3 ) Pub Date : 2019-12-16 , DOI: 10.1039/c9fd00073a Francesco Segatta 1 , Artur Nenov , Silvia Orlandi , Alberto Arcioni , Shaul Mukamel , Marco Garavelli
Faraday Discussions ( IF 3.3 ) Pub Date : 2019-12-16 , DOI: 10.1039/c9fd00073a Francesco Segatta 1 , Artur Nenov , Silvia Orlandi , Alberto Arcioni , Shaul Mukamel , Marco Garavelli
Affiliation
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X-ray spectroscopy is gaining a growing interest in the scientific community, as it represents a versatile and powerful experimental toolbox for probing the dynamics of both core and valence electronic excitations, nuclear motions and material structure, with element and site specificity. Among the various X-ray based techniques, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, which investigates the energy and probability of resonant core-to-valence transitions, has started to be applied to organic molecules: a recent UV-pump X-ray probe time-resolved NEXAFS experiment [Wolf et al., Nat. Commun., 2017, 8, 1] has shown the capability of the technique to provide information about the ultrafast internal conversion between the bright ππ* and the dark nπ* electronic states of the nucleobase thymine. In the present contribution we introduce an accurate theoretical approach for the simulation of NEXAFS spectra of organic molecules, employing azobenzene as a test case. The electronic structure calculations, which provide both energy levels and transition probabilities of core-to-valence excitations, were here performed with a high level multiconfigurational method, the restricted active space self consistent field (RASSCF/RASPT2). GS- and nπ*-NEXAFS spectra were obtained on the top of key molecular geometries (as the optimized cis, trans and conical intersection(s) structures) as well as along the fundamental isomerization coordinates (namely, symmetric and asymmetric bendings of the phenyl rings, and torsion around the central dihedral). We eventually characterize and explain the origin of the simulated signals, highlighting the specific signatures that make it possible to follow the excited state evolution from the nπ* Franck-Condon point, towards the conical intersection(s).
中文翻译：
探索光泵X射线探针NEXAFS光谱学跟踪圆锥形相交介导的光诱导动力学的能力。
X射线光谱学在科学界引起了越来越多的兴趣，因为它代表了一种功能强大且功能强大的实验工具箱，可用于探测核心和价电子激发，核运动和材料结构的动力学，并具有元素和位点特异性。在各种基于X射线的技术中，研究近缘X射线吸收精细结构（NEXAFS）光谱的能量和共振核价转变的可能性已开始应用于有机分子：最近的紫外线泵X射线探针时间分辨NEXAFS实验[Wolf等，Nat。Commun。，2017，8，1]显示了该技术提供有关核碱基胸腺嘧啶的亮ππ*和暗nπ*电子态之间超快内部转换的信息的能力。在当前的贡献中，我们引入了一种精确的理论方法来模拟有机分子的NEXAFS光谱，并以偶氮苯为测试案例。电子结构计算同时提供了能级和价核激发的跃迁几率，在此使用高级多配置方法（受限活动空间自洽场（RASSCF / RASPT2））进行了计算。GS-和nπ* -NEXAFS光谱是在关键分子几何结构的顶部（作为优化的顺式，反式和圆锥形交叉结构）以及基本的异构化坐标（即苯基的对称和不对称弯曲）获得的环和中央二面角周围的扭转）。我们最终将表征和解释模拟信号的起源，
更新日期：2019-12-17
中文翻译：
探索光泵X射线探针NEXAFS光谱学跟踪圆锥形相交介导的光诱导动力学的能力。
X射线光谱学在科学界引起了越来越多的兴趣，因为它代表了一种功能强大且功能强大的实验工具箱，可用于探测核心和价电子激发，核运动和材料结构的动力学，并具有元素和位点特异性。在各种基于X射线的技术中，研究近缘X射线吸收精细结构（NEXAFS）光谱的能量和共振核价转变的可能性已开始应用于有机分子：最近的紫外线泵X射线探针时间分辨NEXAFS实验[Wolf等，Nat。Commun。，2017，8，1]显示了该技术提供有关核碱基胸腺嘧啶的亮ππ*和暗nπ*电子态之间超快内部转换的信息的能力。在当前的贡献中，我们引入了一种精确的理论方法来模拟有机分子的NEXAFS光谱，并以偶氮苯为测试案例。电子结构计算同时提供了能级和价核激发的跃迁几率，在此使用高级多配置方法（受限活动空间自洽场（RASSCF / RASPT2））进行了计算。GS-和nπ* -NEXAFS光谱是在关键分子几何结构的顶部（作为优化的顺式，反式和圆锥形交叉结构）以及基本的异构化坐标（即苯基的对称和不对称弯曲）获得的环和中央二面角周围的扭转）。我们最终将表征和解释模拟信号的起源，
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