We present the first investigation of excited state dynamics by resonant Auger–Meitner spectroscopy (also known as resonant Auger spectroscopy) using the nucleobase thymine as an example. Thymine is photoexcited in the UV and probed with X-ray photon energies at and below the oxygen K-edge. After initial photoexcitation to a ππ* excited state, thymine is known to undergo internal conversion to an nπ* excited state with a strong resonance at the oxygen K-edge, red-shifted from the ground state π* resonances of thymine (see our previous study Wolf, et al., Nat. Commun., 2017, 8, 29). We resolve and compare the Auger–Meitner electron spectra associated both with the excited state and ground state resonances, and distinguish participator and spectator decay contributions. Furthermore, we observe simultaneously with the decay of the nπ* state signatures the appearance of additional resonant Auger–Meitner contributions at photon energies between the nπ* state and the ground state resonances. We assign these contributions to population transfer from the nπ* state to a ππ* triplet state via intersystem crossing on the picosecond timescale based on simulations of the X-ray absorption spectra in the vibrationally hot triplet state. Moreover, we identify signatures from the initially excited ππ* singlet state which we have not observed in our previous study.

中文翻译：

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光激发胸腺嘧啶的瞬态共振俄歇-迈特纳光谱

我们以核碱基胸腺嘧啶为例，通过共振俄歇-迈特纳光谱（也称为共振俄歇光谱）对激发态动力学进行了首次研究。胸腺嘧啶在紫外线中被光激发，并在氧气K边缘及其下方用X射线光子能量探测。最初的光激发到ππ*激发态后，胸腺嘧啶经历内部转换成nπ*激发态，在氧K边缘具有很强的共振，从胸腺嘧啶的基态π*共振红移（请参阅我们的上一篇）研究狼，等人，纳特。COMMUN。，2017年，8，29）。我们解析和比较与激发态和基态共振相关的俄歇-迈特纳电子光谱，并区分参与者和观众的衰变贡献。此外，我们同时观察到nπ*状态签名的衰减，在nπ*状态和基态谐振之间的光子能量处，出现了额外的共振俄歇-迈特纳贡献。我们分配从Nπ人口转移这些贡献*态到ππ*三重态通过基于在振动热三重态的X射线吸收光谱的模拟皮秒的时间尺度系间窜越。此外，我们从最初的激发ππ*单重态中识别出特征，而在先前的研究中我们没有观察到。