rsta20170470_si_001.pdf (9.76 MB)

MO shapes, transition charge densities, attosecond/femtosecond charge migration, and the role of the phase cycling protocol from Imaging of transition charge densities involving carbon core excitations by all X-ray sum-frequency generation

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journal contribution
posted on 25.02.2019 by Daeheum Cho, Jérémy R. Rouxel, Markus Kowalewski, JinYong Lee, Shaul Mukamel
X-ray diffraction signals from the time-evolving molecular charge density induced by selective core excitation of chemically inequivalent carbon atoms are calculated. A narrowband X-ray pulse selectively excites the carbon K-edge of the –CH3 or –CH2F groups in fluoroethane (CH3–CH2F). Each excitation creates a distinct core coherence which depends on the character of the electronic transition. Direct propagation of the reduced single-electron density matrix, using real-time time-dependent density functional theory, provides the time-evolving charge density following interactions with external fields. The interplay between partially filled valence molecular orbitals upon core excitation induces characteristic femtosecond charge migration which depends on the core-valence coherence, and is monitored by the sum-frequency generation diffraction signal.This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.