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ABSTRACT: In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer. The energy resolution (E/ΔE) has been found to be ∼30. Using electrostatic retardation of the electrons, it can be increased to at least 110. The transmission as a function of kinetic energy is flat, and is not impaired much by retardation with up to 80% of the initial kinetic energy. We have measured a detection efficiency of most probably 0.6(-0.1) (+0.05), but at least of 0.4. Results from testing the alignment of the magnet, and from trajectory simulations, are also discussed.
The Review of scientific instruments 06/2012; 83(6):063106. · 1.52 Impact Factor
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L Lammich,
C Domesle,
B Jordon-Thaden,
M Förstel, T Arion,
T Lischke,
O Heber,
S Klumpp,
M Martins,
N Guerassimova,
R Treusch,
J Ullrich,
U Hergenhahn,
H B Pedersen,
A Wolf
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ABSTRACT: Photofragmentation of the protonated water dimer H+(H2O)_{2}, a fundamental system both in aqueous solutions and gas-phase water clusters, has been studied at 13.8 nm using the Free Electron Laser FLASH in Hamburg. In a crossed-beam experiment using time-resolved, single-molecule fragment imaging, the two-body breakup into H2O++H3O+ was found as a prominent fragmentation channel with a kinetic energy release of up to 10 eV. This channel was observed with at least a similar yield as events with stronger fragmentation, producing protons together with neutral fragments and showing an absolute cross section of (0.5 ± 0.2) × 10(-18) cm2.
Physical Review Letters 12/2010; 105(25):253003. · 7.37 Impact Factor
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The Journal of Chemical Physics, v.134 (2011).
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L. Lammich,
C. Domesle,
B. Jordon-Thaden,
M. F"orstel, T. Arion,
T. Lischke,
O. Heber,
S. Klumpp,
M. Martins,
N. Guerassimova,
R. Treusch,
J. Ullrich,
U. Hergenhahn,
H B Pedersen,
A Wolf
Phys. Rev. Lett. 105(2010),253003.
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Physical Review B, v.82 (2010).
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ABSTRACT: We present high-resolution photoelectron–Auger-electron coincidence spectra of methane (CH4). Since the vibrational structure in the photoelectron spectrum is resolved, the Auger spectra corresponding to different vibrational levels can be separated. The seven final states of CH42+ are either dissociative or metastable, but in any case are populated in a repulsive part of their potential-energy curve via the Auger decay. The Auger line shapes can therefore be obtained by mapping the vibrational wave functions of the core-hole state into energy space. We have implemented this connection in the data analysis. By simultaneously fitting the different Auger spectra, detailed information on the energies of the dicationic states and their repulsive potential-energy curves is derived.
Phys. Rev. A. 83(4).
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ABSTRACT: Low-energy electrons are the most abundant product of ionizing radiation in condensed matter. The origin of these electrons is most commonly understood to be secondary electrons1 ionized from core or valence levels by incident radiation and slowed by multiple inelastic scattering events. Here, we investigate the production of low-energy electrons in amorphous medium-sized water clusters, which simulate water molecules in an aqueous environment. We identify a hitherto unrecognized extra source of low-energy electrons produced by a non-local autoionization process called intermolecular coulombic decay2 (ICD). The unequivocal signature of this process is observed in coincidence measurements of low energy electrons and photoelectrons generated from inner-valence states with vacuum-ultraviolet light. As ICD is expected to take place universally in weakly bound aggregates containing light atoms between carbon and neon in the periodic table2,3, these results could have implications for our understanding of ionization damage in living tissues.
Nature Physics (2010).
