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Download fileOrigin of Dark-Channel X-ray Fluorescence from Transition-Metal Ions in Water
journal contribution
posted on 2012-01-25, 00:00 authored by Robert Seidel, Samira Ghadimi, Kathrin
M. Lange, Sébastien Bonhommeau, Mikhail A. Soldatov, Ronny Golnak, Alexander Kothe, René Könnecke, Alexander Soldatov, Stephan Thürmer, Bernd Winter, Emad F. AzizThe nonradiative dark channels in the L-edge fluorescence
spectra
from transition-metal aqueous solution identify the ultrafast charge-transfer
processes playing an important role in many biological and chemical
systems. Yet, the exact origin of such spectral dips with respect
to the X-ray transmission spectrum has remained unclear. In the present
study we explore the nature of the underlying decay mechanism of 2p
core-excited Co2+ in water by probing the nonradiative
Auger-type electron emission channel using photoelectron spectroscopy
from a liquid microjet. Our measurements demonstrate unequivocally
that metal-to-water charge transfer quenches fluorescence and will
inevitably lead to a dip in the total-fluorescence-yield X-ray absorption
spectrum. This is directly revealed from the resonant enhancement
of valence signal intensity arising from the interference of two identical
final states created by a direct and Auger-electron emission, respectively.