Attosecond X-ray Diffraction Triggered by Core or Valence Ionization of a Dipeptide
Attosecond X-ray Diffraction Triggered by Core or Valence Ionization of a Dipeptide
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DOI：
10.1021/acs.jctc.7b00920
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发表时间：
2018-01-01
影响因子：
5.5
通讯作者：
Mukamel, Shaul
中科院分区：
文献类型：
--
作者：
Cho, Daeheum;Rouxel, Jeremy R.;Mukamel, Shaul
随着强超快x射线源的进步，现在可以通过时间分辨x射线衍射实时和真实空间跟踪电子动力学来创建分子电影。本文采用实时时变密度泛函理论（RT-TDDFT）模拟甘氨酸-苯丙氨酸（GF）二肽发生脉冲核或价电离后的电子动力学。计算了随时间变化的偶极矩、电荷密度和时间分辨的x射线衍射信号。价电离的电荷振荡计算为7fs，核电离计算为500 fs。电荷振荡的时间尺度与苯丙氨酸单体相当（4 fs） [Science 2014, 346,336]，并且由于甘氨酸链的拉长而稍长一些。在价电离之后，电荷在GF上的迁移是由富电子酰胺基团的氧和氮的离域孤对轨道介导的。偶极矩的时间傅里叶变换提供了电荷迁移动力学和所涉及的分子轨道的详细信息。外差探测到的阿秒x射线衍射信号提供了动量空间中散射幅度的大小和相位，从而可以反向得到实空间中的电荷密度。
With the advancement of intense ultrafast X-ray sources, it is now possible to create a molecular movie by following the electronic dynamics in real time and real space through time-resolved X-ray diffraction. Here we employ real-time time-dependent density functional theory (RT-TDDFT) to simulate the electronic dynamics after an impulse core or valence ionization in the glycine-phenylalanine (GF) dipeptide. The time-evolving dipole moment, the charge density, and the time-resolved X-ray diffraction signals are calculated. The charge oscillation is calculated for 7 fs for valence ionization and 500 as for core ionization. The charge oscillation time scale is comparable to that found in a phenylalanine monomer (4 fs) [Science 2014, 346, 336] and is slightly longer because of the elongated glycine chain. Following valence ionization, the charge migration across the GF is mediated by the delocalized lone-pair orbitals of oxygen and nitrogen of the electron-rich amide group. The temporal Fourier transform of the dipole moment provides detailed information on the charge migration dynamics and the molecular orbitals involved. Heterodyne-detected attosecond X-ray diffraction signals provide the magnitude and phase of the scattering amplitude in momentum space and can thus be inverted to yield the charge density in real space.