title: Ultrafast extreme ultraviolet induced isomerization of acetylene cations.
abstract: Ultrafast isomerization of acetylene cations ([HC=CH](+)) in the low-lying excited A(2)Σ(g)(+) state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C(+) + CH2(+) as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15 fs in a kinetic energy release (KER) window of 5.8<KER<8 eV, providing clear evidence for the existence of a fast, nonradiative decay channel.
authors.affiliation: Max-Planck-Institut für Kernphysik, Heidelberg, Germany.
authors.forename: Y H
authors.initials: YH
authors.lastname: Jiang
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authors.initials: A
authors.lastname: Rudenko
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authors.lastname: Herrwerth
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authors.lastname: Foucar
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authors.lastname: Kurka
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authors.lastname: Kühnel
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authors.lastname: Lezius
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authors.lastname: Kling
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authors.lastname: van Tilborg
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authors.lastname: Belkacem
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authors.lastname: Düsterer
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authors.lastname: Treusch
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authors.initials: CD
authors.lastname: Schröter
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authors.lastname: Moshammer
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authors.lastname: Ullrich