TY  - JOUR
A1  - Leitner, T.
A1  - Josefsson, Ida
A1  - Mazza, T.
A1  - Miedema, Piter S.
A1  - Schröder, H.
A1  - Beye, Martin
A1  - Kunnus, Kristjan
A1  - Schreck, S.
A1  - Düsterer, Stefan
A1  - Föhlisch, Alexander
A1  - Meyer, M.
A1  - Odelius, Michael
A1  - Wernet, Philippe
T1  - Time-resolved electron spectroscopy for chemical analysis of photodissociation
BT  - Photoelectron spectra of Fe(CO)(5), Fe(CO)(4), and Fe(CO)(3)
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The prototypical photoinduced dissociation of Fe(CO)(5) in the gas phase is used to test time-resolved x-ray photoelectron spectroscopy for studying photochemical reactions. Upon one-photon excitation at 266 nm, Fe(CO)(5) successively dissociates to Fe(CO)(4) and Fe(CO)(3) along a pathway where both fragments retain the singlet multiplicity of Fe(CO)(5). The x-ray free-electron laser FLASH is used to probe the reaction intermediates Fe(CO)(4) and Fe(CO)(3) with time-resolved valence and core-level photoelectron spectroscopy, and experimental results are interpreted with ab initio quantum chemical calculations. Changes in the valence photoelectron spectra are shown to reflect changes in the valenceorbital interactions upon Fe-CO dissociation, thereby validating fundamental theoretical concepts in Fe-CO bonding. Chemical shifts of CO 3 sigma inner-valence and Fe 3 sigma core-level binding energies are shown to correlate with changes in the coordination number of the Fe center. We interpret this with coordination-dependent charge localization and core-hole screening based on calculated changes in electron densities upon core-hole creation in the final ionic states. This extends the established capabilities of steady-state electron spectroscopy for chemical analysis to time-resolved investigations. It could also serve as a benchmark for howcharge and spin density changes in molecular dissociation and excited-state dynamics are expressed in valence and core-level photoelectron spectroscopy. Published by AIP Publishing.
Y1  - 2018
U6  - https://doi.org/10.1063/1.5035149
SN  - 0021-9606
SN  - 1089-7690
VL  - 149
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Holldack, Karsten
A1  - Ovsyannikov, Ruslan
A1  - Kuske, P.
A1  - Mueller, R.
A1  - Schaelicke, A.
A1  - Scheer, M.
A1  - Gorgoi, Mihaela
A1  - Kuehn, D.
A1  - Leitner, T.
A1  - Svensson, S.
A1  - Martensson, N.
A1  - Föhlisch, Alexander
T1  - Single bunch X-ray pulses on demand from a multi-bunch synchrotron radiation source
JF  - Nature Communications
N2  - Synchrotron radiation facilities routinely operate in a multi-bunch regime, but applications relying on time-of-flight schemes require single bunch operation. Here we show that pulse picking by resonant excitation in a storage ring creates in addition to the multi-bunch operation a distinct and separable single bunch soft X-ray source. It has variable polarization, a photon flux of up to 10(7)-10(9) ph s(-1)/0.1%BW at purity values of 10(4)-10(2) and a repetition rate of 1.25 MHz. The quasi-resonant excitation of incoherent betatron oscillations of electrons allows horizontal pulse separation at variable (also circular) polarization accessible for both, regular 30 ps pulses and ultrashort pulses of 2-3 ps duration. Combined with a new generation of angularly resolving electron spectrometers this creates unique opportunities for time-resolved photoemission studies as confirmed by time-of-flight spectra. Our pulse picking scheme is particularly suited for surface physics at diffraction-limited light sources promising ultimate spectral resolution.
Y1  - 2014
U6  - https://doi.org/10.1038/ncomms5010
SN  - 2041-1723
VL  - 5
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wernet, Philippe
A1  - Leitner, T.
A1  - Josefsson, Ida
A1  - Mazza, T.
A1  - Miedema, P. S.
A1  - Schroder, H.
A1  - Beye, Martin
A1  - Kunnus, K.
A1  - Schreck, S.
A1  - Radcliffe, P.
A1  - Dusterer, S.
A1  - Meyer, M.
A1  - Odelius, Michael
A1  - Fohlisch, Alexander
T1  - Communication: Direct evidence for sequential dissociation of gas-phase Fe(CO)(5) via a singlet pathway upon excitation at 266 nm
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We prove the hitherto hypothesized sequential dissociation of Fe(CO)(5) in the gas phase upon photoexcitation at 266 nm via a singlet pathway with time-resolved valence and core-level photoelectron spectroscopy with an x-ray free-electron laser. Valence photoelectron spectra are used to identify free CO molecules and to determine the time constants of stepwise dissociation to Fe(CO)(4) within the temporal resolution of the experiment and further to Fe(CO)(3) within 3 ps. Fe 3p core-level photoelectron spectra directly reflect the singlet spin state of the Fe center in Fe(CO)(5), Fe(CO)(4), and Fe(CO)(3) showing that the dissociation exclusively occurs along a singlet pathway without triplet-state contribution. Our results are important for assessing intra- and intermolecular relaxation processes in the photodissociation dynamics of the prototypical Fe(CO)(5) complex in the gas phase and in solution, and they establish time-resolved core-level photoelectron spectroscopy as a powerful tool for determining the multiplicity of transition metals in photochemical reactions of coordination complexes. Published by AIP Publishing.
Y1  - 2017
U6  - https://doi.org/10.1063/1.4984774
SN  - 0021-9606
SN  - 1089-7690
VL  - 146
PB  - American Institute of Physics
CY  - Melville
ER  -