The Variable Polarization XUV Beamline P04 at PETRA III: Optics, mechanics and their performance

Viefhaus, Jens; Scholz, Frank; Deinert, Sascha; Glaser, Leif; Ilchen, Markus; Seltmann, Jörn; Walter, Peter; Siewert, Frank

doi:10.1016/j.nima.2012.10.110

Cited by 173 publications

(159 citation statements)

References 7 publications

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“…For the present experiment the photon-ion mergedbeams technique was employed using the permanently installed end station PIPE [16] at the "Variable Polarization XUV Beamline" (P04) [17] of the synchrotron light source PETRA III at DESY in Hamburg, Germany. Negatively charged oxygen ions were produced from a gas mixture of O 2 and He in an electron-cyclotron resonance (ECR) ion source.…”

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Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

et al. 2016

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The photon-ion merged-beams technique was used at a synchrotron light source for measuring absolute cross sections of double and triple photodetachment of O − ions. The experimental photon energy range of 524-543 eV comprised the threshold for K-shell ionization. Using resolving powers of up to 13000, the position, strength and width of the below-threshold 1s 2s 2 2p 6 2 S resonance as well as the positions of the 1s 2s 2 2p 5 3 P and 1s 2s 2 2p 5 1 P thresholds for K-shell ionization were determined with high-precision. In addition, systematically enlarged multi-configuration Dirac-Fock calculations have been performed for the resonant detachment cross sections. Results from these abinitio computations agree very well with the measurements for the widths and branching fractions for double and triple detachment, if double shake-up (and -down) of the valence electrons and the rearrangement of the electron density is taken into account. For the absolute cross sections, however, a previously found discrepancy between measurements and theory is confirmed. Negative atomic ions play an important role in lowtemperature plasmas such as the upper atmosphere or the interstellar medium [1] and also in technical applications. For example, in the context of antihydrogen production, it has been proposed to use an ensemble of laser-cooled anions as a coolant for antiprotons [2]. Negative ions are fundamentally different from neutral atoms or positive ions since the extra electron in a negative ion is not only bound by the long-range Coulomb interaction with the atomic nucleus but, more importantly, also by a short-range attractive force due to the polarization of the atomic core. The accurate theoretical description of these ions still challenges the state-of-the-art quantum computations although the numbers of their bound states are generally finite. The low-excitation levels of negative ions are readily accessible by laser spectroscopy (see, e.g., [3][4][5][6]). Therefore, this technique has been a prime source of experimental information about the mutual interactions among the valence electrons.A sensitive tool for studying the interactions between the valence and the core electrons is inner-shell ionization of negative ions [7,8]. Here, we apply the photon-ion merged-beams technique (see [9] for a recent overview) to determine the absolute cross sections for double and triple ionization (detachment) of oxygen anions in the photon energy range 524-543 eV. In this energy range, a K-shell vacancy may be produced either by direct ionization of an initial 1s electron or via the formation of a resonance state by exciting one 1s electron to a higher shell such as 2p. In either case, the K-vacancy decays subsequently by a cascade of radiative and nonradiative processes leading to a distribution of final charge states with O + and O 2+ as the most prominent charged reaction products. To test and better understand the theoretical prediction of such cascades, we performed extremely comprehensive quantum calculations for the formation...

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Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

et al. 2016

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“…As reported previously 23 , this procedure results in a significant Se/Te substitution at the surface. The XPS and XAS measurements were performed in the ASPHERE III endstation, using a Scienta R4000 electron analyzer, with an energy resolution better than 200 meV, at the XUV beamline P04 of PETRA III (DESY, Hamburg) 24 , at a base pressure of 3 × 10 −10 mbar.…”

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Impurity states in the magnetic topological insulator V:(Bi,Sb)2Te3

et al. 2016

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The ferromagnetic topological insulator V:(Bi,Sb) 2 Te 3 has been recently reported as a quantum anomalous Hall (QAH) system. Yet the microscopic origins of the QAH effect and the ferromagnetism remain unclear. One key aspect is the contribution of the V atoms to the electronic structure. Here the valence band of V:(Bi,Sb) 2 Te 3 thin films was probed in an element-specific way by resonant photoemission spectroscopy. The signature of the V 3d impurity band was extracted and exhibits a high density of states near Fermi level, in agreement with spin-polarized first-principles calculations. Our results indicate the occurrence of a ferromagnetic superexchange interaction mediated by the observed impurity band, contributing to the ferromagnetism in this system.

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“…The experiment was performed at the P04 beamline of the synchrotron-light facility PE-TRA III at DESY in Hamburg, 43 providing a photon beam with a micro-focus of 5×10 µm 2 .…”

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confidence: 99%

Optical Fluorescence Detected from X-ray Irradiated Liquid Water

et al. 2017

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Despite its importance, the structure and dynamics of liquid water are still poorly understood in many apsects. Here, we report on the observation of optical fluorescence upon soft X-ray irradiation of liquid water. Detection of spectrally resolved fluorescence was achieved by a combination of the liquid microjet technique and fluorescence spectroscopy. We observe a genuine liquid-phase fluorescence manifested by a broad emission band in the 170 to 340 nm (4-7 eV) photon wavelength range. In addition, another narrower emission near 300 nm can be assigned to the fluorescence of OH(A state) in the gas phase, the emitting species being formed by Auger electrons escaping from liquid water. We argue that the newly observed broad-band emission of liquid water is relevant in search of extraterrestrial life, and we also envision the observed electronejection mechanism to find application for exploring solutes at liquid-vapor interfaces.

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The Variable Polarization XUV Beamline P04 at PETRA III: Optics, mechanics and their performance

Cited by 173 publications

References 7 publications

Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

Prominent role of multielectron processes inK-shell double and triple photodetachment of oxygen anions

Impurity states in the magnetic topological insulator V:(Bi,Sb)2Te3

Optical Fluorescence Detected from X-ray Irradiated Liquid Water

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