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Dive into the research topics where A. Langenberg is active.

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Featured researches published by A. Langenberg.


Journal of Chemical Physics | 2011

Communication: Highest occupied molecular orbital–lowest unoccupied molecular orbital gaps of doped silicon clusters from core level spectroscopy

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

Maximum Spin Polarization in Chromium Dimer Cations as Demonstrated by X‐ray Magnetic Circular Dichroism Spectroscopy

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

Large orbital magnetic moments of small, free cobalt cluster ions Co n + with n ≤ 9

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

2p core-level binding energies of size-selected free silicon clusters

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

Initial- and final-state effects on screening and branching ratio in2px-ray absorption of size-selected free3dtransition metal clusters

K. Hirsch; V. Zamudio-Bayer; J. Rittmann; A. Langenberg; M. Vogel; T. Möller; Bernd von Issendorff; J. T. Lau


Physical Review B | 2009

Localized high spin states in transition-metal dimers: X-ray absorption spectroscopy study

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

2px-ray absorption of free transition-metal cations across the 3dtransition elements: Calcium through copper

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

Higher Ionization Energies from Sequential Vacuum-Ultraviolet Multiphoton Ionization of Size-Selected Silicon Cluster Cations

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

Impurity Electron Localization in Early-Transition-Metal-Doped Gold Clusters

K. Hirsch; V. Zamudio-Bayer; A. Langenberg; M. Vogel; J. Rittmann; S. Forin; T. Möller; Bernd von Issendorff; J. T. Lau


Angewandte Chemie | 2015

Nachweis maximaler Spinpolarisation in Chromdimerkationen durch zirkularen magnetischen Röntgendichroismus

V. Zamudio-Bayer; K. Hirsch; A. Langenberg; Markus Niemeyer; M. Vogel; Arkadiusz Ławicki; Akira Terasaki; J. Tobias Lau; Bernd von Issendorff

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K. Hirsch

Technical University of Berlin

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M. Vogel

Helmholtz-Zentrum Berlin

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J. Rittmann

Technical University of Berlin

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T. Möller

Technical University of Berlin

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J. T. Lau

Technical University of Berlin

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J. Tobias Lau

Helmholtz-Zentrum Berlin

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