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Attosecond X-ray Diffraction Triggered by Core or Valence Ionization of a Dipeptide.
- Source :
-
Journal of chemical theory and computation [J Chem Theory Comput] 2018 Jan 09; Vol. 14 (1), pp. 329-338. Date of Electronic Publication: 2017 Dec 06. - Publication Year :
- 2018
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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.
Details
- Language :
- English
- ISSN :
- 1549-9626
- Volume :
- 14
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Journal of chemical theory and computation
- Publication Type :
- Academic Journal
- Accession number :
- 29140696
- Full Text :
- https://doi.org/10.1021/acs.jctc.7b00920