Formative period in the x-ray-induced photodissociation of organic molecules
Formative period in the x-ray-induced photodissociation of organic molecules
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X 射线诱导有机分子光解的形成期
DOI：
10.1103/physrevresearch.3.013221
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发表时间：
2021
影响因子：
4.2
通讯作者：
Kiyoshi Ueda
中科院分区：
文献类型：
--
作者：
Edwin Kukk;Hironobu Fukuzawa;Niskanen Johannes;Kiyonobu Nagaya;Kooser Kuno;Daehyun You;Jasper Peschel;Sylvain Maclot;Akinobu Niozu;Shu Saito;Yu Luo;Eetu Pelimanni;Itala Eero; John D Bozek;Tsukasa Takanashi;Marta Berholts;Per Johnsson; Kiyoshi Ueda
轻元素有机物和生物分子的原子内壳层对x射线光子的吸收常常导致指示电子态的形成和分子断裂。利用超光子环-8 GeV （SPring-8）埃紧凑型自由电子激光器（SACLA）的飞秒x射线脉冲，研究了具有代表性的中型有机分子噻吩的x射线诱导解离景观。由光发射在硫轨道上产生的空穴被俄歇过程填满，俄歇过程在广泛的内能范围内产生了指示的分子状态——这是x射线诱导动力学的一个特殊起点。利用近红外（800 nm）激光脉冲泵浦探针实验监测了电离分子的演变。离子-离子重合和离子动量分析表明，环的多体破裂增加了离子碎片的产率，这归因于指示母分子状态的高激发部分的额外电离。在160-fs的时间常数范围内，增强的瞬态性质和衰减表明了开环亲本几何结构的形成和亲本物种在分离事件发生前的统计存活时间。通过近红外光探测瞬态、高激发性质的特定俄歇最终状态，我们展示了在x射线诱导的有机分子和生物分子损伤早期，泵浦探针特征如何与动力学中的关键特征相关。
Absorption of x-ray photons by atomic inner shells of light-element organics and biomolecules often leads to formation of dicationic electronic states and to molecular fragmentation. We investigated the x-ray-induced dissociation landscape of a representative medium-sized organic molecule, thiophene, by femtosecond x-ray pulses from the Super Photon Ring-8 GeV (SPring-8) Angstrom Compact Free-Electron Laser (SACLA). Holes, created in the sulfurorbital by photoemission, were filled by the Auger process that created dicationic molecular states within a broad range of internal energies—a starting point particular to x-ray-induced dynamics. The evolution of the ionized molecules was monitored by a pump-probe experiment using a near-infrared (800 nm) laser pulse. Ion-ion coincidence and ion momentum analysis reveals enhanced yields of ionic fragments from multibody breakup of the ring, attributed to additional ionization of the highly excited fraction of the dicationic parent molecular states. The transient nature of the enhancement and its decay with about a 160-fs time constant indicate formation of an open-ring parent geometry and the statistical survival time of the parent species before the dissociation events. By probing specific Auger final states of transient, highly excited nature by near-infrared light, we demonstrate how pump-probe signatures can be related to the key features in dynamics during the early period of the x-ray-induced damage of organic molecules and biomolecules.