Ultra-Fast-VUV Photoemission Study of UV Excited 2-Nitrophenol
Ultra-Fast-VUV Photoemission Study of UV Excited 2-Nitrophenol
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DOI：
10.1021/acs.jpca.8b10136
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发表时间：
2019-02-21
影响因子：
2.9
通讯作者：
Piccirillo, Susanna
中科院分区：
文献类型：
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作者：
Ciavardini, Alessandra;Coreno, Marcello;Piccirillo, Susanna
采用时间分辨光电子能谱 (TRPES) 和单色高次谐波发生源产生的飞秒真空紫外光研究了在 268 nm 激发的气态 2-硝基苯酚的初始失活路径。 TRPES 使我们能够获得有关 2-硝基苯酚在气相中的超快激发态动力学的新的、有价值的实验信息。根据最近的从头算动态非绝热分子动力学模拟，我们的结果验证了超快系间穿越的发生，导致中间态在亚皮秒时间尺度上通过分支机制衰减。实验观察到两种衰变途径。其中一种可能涉及质子转移，从而产生最稳定的三重态酸形式的 2-硝基苯酚；第二条途径可能涉及 OH 旋转。我们认为，在系统间穿越之后，导致 OH 或 HONO 丢失的超快碎片通道也可能起作用。
The initial deactivation pathways of gaseous 2-nitrophenol excited at 268 nm were investigated by time-resolved photoelectron spectroscopy (TRPES) with femtosecond-VUV light, produced by a monochromatized high harmonic generation source. TRPES allowed us to obtain new, valuable experimental information about the ultrafast excited-state dynamics of 2-nitrophenol in the gas phase. In accord with recent ab initio on-the-fly nonadiabatic molecular dynamic simulations, our results validate the occurrence of an ultrafast intersystem crossing leading to an intermediate state that decays on a subpicosecond time scale with a branched mechanisms. Two decay pathways are experimentally observed. One probably involves proton transfer, leading to the most stable triplet aci-form of 2-nitrophenol; the second pathway may involve OH rotation. We propose that following intersystem crossing, an ultrafast fragmentation channel leading to OH or HONO loss could also be operative.