Abstract

X-ray free-electron lasers (XFELs) are a source of high brightness x-ray pulses with continuously tunable wavelength across the soft x-ray regime. At these wavelengths it is possible to address core-to-valence transitions in molecules containing carbon, nitrogen, oxygen and other small atoms. In a molecular or condensed phase system, the strength of these transitions is strongly localized to the vicinity of the relevant atom. This offers the possibility to drive and interrogate valence electron dynamics in such systems using soft x-rays, with atomic site spatial sensitivity.

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