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Imaging of transition charge densities involving carbon core excitations by all X-ray sum-frequency generation.


ABSTRACT: 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'.

SUBMITTER: Cho D 

PROVIDER: S-EPMC6452053 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Imaging of transition charge densities involving carbon core excitations by all X-ray sum-frequency generation.

Cho Daeheum D   Rouxel Jérémy R JR   Kowalewski Markus M   Lee JinYong J   Mukamel Shaul S  

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 20190501 2145


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 -CH<sub>3</sub> or -CH<sub>2</sub>F groups in fluoroethane (CH<sub>3</sub>-CH<sub>2</sub>F). Each excitation creates a distinct core coherence which depends on the character of the electronic transition. Direct propagation of the reduced single-electron density m  ...[more]

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