A. Langenberg
Helmholtz-Zentrum Berlin
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Featured researches published by A. Langenberg.
Journal of Chemical Physics | 2011
J. T. Lau; M. Vogel; A. Langenberg; K. Hirsch; J. Rittmann; V. Zamudio-Bayer; T. Möller; B. von Issendorff
A method to determine band gaps of size-selected and isolated nanoparticles by combination of valence band and core-level photoionization spectroscopy is presented. This approach is widely applicable and provides a convenient alternative to current standard techniques for the determination of band gaps by optical or photoelectron spectroscopy. A first application to vanadium doped silicon clusters confirms a striking size-dependence of their highest occupied-lowest unoccupied molecular orbital gaps.
Angewandte Chemie | 2015
V. Zamudio-Bayer; K. Hirsch; A. Langenberg; Markus Niemeyer; M. Vogel; Arkadiusz Ławicki; Akira Terasaki; J. Tobias Lau; Bernd von Issendorff
X-ray magnetic circular dichroism spectroscopy has been used to characterize the electronic structure and magnetic moment of Cr2 (+) . Our results indicate that the removal of a single electron from the 4sσg bonding orbital of Cr2 drastically changes the preferred coupling of the 3d electronic spins. While the neutral molecule has a zero-spin ground state with a very short bond length, the molecular cation exhibits a ferromagnetically coupled ground state with the highest possible spin of S=11/2, and almost twice the bond length of the neutral molecule. This spin configuration can be interpreted as a result of indirect exchange coupling between the 3d electrons of the two atoms that is mediated by the single 4s electron through a strong intraatomic 3d-4s exchange interaction. Our finding allows an estimate of the relative energies of two states that are often discussed as ground-state candidates, the ferromagnetically coupled (12) Σ and the low-spin (2) Σ state.
Journal of Physics: Condensed Matter | 2018
V. Zamudio-Bayer; K. Hirsch; A. Langenberg; Arkadiusz Lawicki; Akira Terasaki; Bernd von Issendorff; J. Tobias Lau
The size dependent electronic structure and separate spin and orbital magnetic moments of free eo;t (n = 4 9) cluster ions have been invest igated by x-ray ab orption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. A very large orbital magnetic moment of 1.4 ± 0.1 /.LB per atom was determined for Cot , which is one order of magnitude larger than in the bulk metal. Large orbital magnetic moments per atom of~ 1 /.LB were also determined for CoJ , Cot , and Cot. The orbital contribution to the total magnetic moment shows a non-monotonic cluster sizo dependence: T he orbital contribution increases from a local minimum at n = 2 to a local maximum at n = 5 and then decreases with increasing cluster size. The 3d spin magnetic moment per atom is nearly constant and is solely defined by the number of 3d holes which shows that t he 3d majority ~pin states arc fully occupied , that is, 3d hole spin polarization is 100%. K eywords: orbital magnetic moment, XMCD, cobalt clusters, spin magnetic moment, magnetic anisotropy energy, spin polarization
Physical Review B | 2012
M. Vogel; Christian Kasigkeit; K. Hirsch; A. Langenberg; J. Rittmann; V. Zamudio-Bayer; Alexander Kulesza; Roland Mitrić; T. Möller; B. von Issendorf; J. T. Lau
Physical Review B | 2012
K. Hirsch; V. Zamudio-Bayer; J. Rittmann; A. Langenberg; M. Vogel; T. Möller; Bernd von Issendorff; J. T. Lau
Physical Review B | 2009
J. T. Lau; K. Hirsch; A. Langenberg; J. Probst; R. Richter; J. Rittmann; M. Vogel; V. Zamudio-Bayer; T. Möller; B. von Issendorff
Physical Review A | 2012
K. Hirsch; V. Zamudio-Bayer; F. Ameseder; A. Langenberg; J. Rittmann; M. Vogel; T. Möller; Bernd von Issendorff; J. T. Lau
Journal of Physical Chemistry C | 2015
Christian Kasigkeit; K. Hirsch; A. Langenberg; T. Möller; Jürgen Probst; J. Rittmann; M. Vogel; Jörg Wittich; V. Zamudio-Bayer; Bernd von Issendorff; J. Tobias Lau
Journal of Physical Chemistry C | 2015
K. Hirsch; V. Zamudio-Bayer; A. Langenberg; M. Vogel; J. Rittmann; S. Forin; T. Möller; Bernd von Issendorff; J. T. Lau
Angewandte Chemie | 2015
V. Zamudio-Bayer; K. Hirsch; A. Langenberg; Markus Niemeyer; M. Vogel; Arkadiusz Ławicki; Akira Terasaki; J. Tobias Lau; Bernd von Issendorff