Attosecond X-ray Diffraction Triggered by Core or Valence Ionization of a Dipeptide
- 6 December 2017
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of Chemical Theory and Computation
- Vol. 14 (1), 329-338
- https://doi.org/10.1021/acs.jctc.7b00920
Abstract
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.Keywords
Funding Information
- Division of Chemistry (CHE-1663822)
- Basic Energy Sciences (DE-FG02-04ER15571)
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