J. Braun

Publications (34)23.63 Total impact

• Article: High-precision laser-assisted absolute determination of x-ray diffraction angles.

  K Kubicek, J Braun, H Bruhns, J R Crespo López-Urrutia, P H Mokler, J Ullrich
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  ABSTRACT: A novel technique for absolute wavelength determination in high-precision crystal x-ray spectroscopy recently introduced has been upgraded reaching unprecedented accuracies. The method combines visible laser beams with the Bond method, where Bragg angles (θ and -θ) are determined without any x-ray reference lines. Using flat crystals this technique makes absolute x-ray wavelength measurements feasible even at low x-ray fluxes. The upgraded spectrometer has been used in combination with first experiments on the 1s2p(1)P(1) → 1s(2)(1)S(0) w-line in He-like argon. By resolving a minute curvature of the x-ray lines the accuracy reaches there the best ever reported value of 1.5 ppm. The result is sensitive to predicted second-order QED contributions at the level of two-electron screening and two-photon radiative diagrams and will allow for the first time to benchmark predicted binding energies for He-like ions at this level of precision.
  The Review of scientific instruments 01/2012; 83(1):013102. · 1.52 Impact Factor
• Article: Two-loop QED contributions tests with mid-Z He-like ions

  K. Kubiček, H. Bruhns, J. Braun
  Journal of Physics: …. 01/2009;
• Article: Single-electron capture in keV Ar15+...18++He collisions

  S. Knoop, D. Fischer, Y. Xue, M. Zapukhlyak, C.J. Osborne, Th. Ergler, T. Ferger, J. Braun, G. Brenner, H. Bruhns, [......], S.W. Epp, A.J.G. Martínez, G. Sikler, R.S. Orts, H. Tawara, T. Kirchner, J.R.C. López-Urrutia, R. Moshammer, J. Ullrich, R. Hoekstra
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  ABSTRACT: Export Date: 23 October 2011, Source: Scopus, Art. No.: 195203, CODEN: JPAPE, doi: 10.1088/0953-4075/41/19/195203
  Journal of Physics B: Atomic, Molecular and Optical Physics. 01/2008; 41.
• Article: Testing QED screening and two-loop contributions with He-Like ions.

  H Bruhns, J Braun, K Kubicek, J R Crespo López-Urrutia, J Ullrich
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  ABSTRACT: We report wavelength measurements of H-like and He-like ions obtained with a novel x-ray spectrometer at the Heidelberg Electron Beam Ion Trap. The experimental uncertainty for the Lyman-alpha1 wavelength in Cl16+ is reduced by a factor of 3 and, as expected, excellent agreement with theory is maintained. For the resonance line in He-like Ar16+, an uncertainty of only deltalambda/lambda=2x10(-6) was achieved. This is the most precise x-ray wavelength reported for highly charged ions to date, and allows to test recent predictions on QED two-electron and two-photon radiative corrections for He-like ions. The results also point to the advantages of establishing absolute x-ray wavelength standards using Lyman-alpha transitions (in the present case Ar17+ Lyman-alpha1) to supersede the current ones.
  Physical Review Letters 10/2007; 99(11):113001. · 7.37 Impact Factor
• Article: Testing QED Screening and Two-Loop Contributions with He-Like Ions

  H. Bruhns, J. Braun, K. Kubiček
  Physical review letters. 01/2007;
• Article: High precision X-ray spectroscopy on H-and He-like Argon Ions

  H. Bruhns, J. Braun, J.R.C. López-Urrutia, J. Ullrich
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  ABSTRACT: Export Date: 23 October 2011, Source: Scopus, Art. No.: 012016, doi: 10.1088/1742-6596/72/1/012016
  Journal of Physics: Conference Series. 01/2007; 72.
• Article: Testing QED screening and two-loop contributions with He-like ions

  H. Bruhns, J. Braun, K. Kubiček, J.R. Crespo López-Urrutia, J. Ullrich
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  ABSTRACT: Cited By (since 1996): 10, Export Date: 23 October 2011, Source: Scopus, Art. No.: 113001, CODEN: PRLTA, doi: 10.1103/PhysRevLett.99.113001
  Physical Review Letters. 01/2007; 99.
• Article: Benchmarking high-field few-electron correlation and QED contributions in Hg^{75+} to Hg^{78+} ions. I. Experiment

  A. J. González Martínez, J. R. Crespo López-Urrutia, J. Braun, G. Brenner, H. Bruhns, A. Lapierre, V. Mironov, R. Soria Orts, H. Tawara, M. Trinczek, J. Ullrich, A. N. Artemyev, Z. Harman, U. D. Jentschura, C. H. Keitel, J. H. Scofield, I. I. Tupitsyn
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  ABSTRACT: The photorecombination of highly charged few-electron mercury ions Hg75+ to Hg78+ has been explored with the Heidelberg electron beam ion trap. By monitoring the emitted x rays (65–76 keV) and scanning the electron beam energy (45–54 keV) over the KLL dielectronic recombination (DR) region, the energies of state-selected DR resonances were determined to within ±4 eV (relative) and ±14 eV (absolute). At this level of experimental accuracy, it becomes possible to make a detailed comparison to various theoretical approaches and methods, all of which include quantum electrodynamic (QED) effects and finite nuclear size contributions (for a 1s electron, these effects can be as large as 160 and 50 eV, respectively). In He-like Hg78+, a good agreement between the experimental results and the calculations has been found. However, for the capture into Li-, Be-, and B-like ions, significant discrepancies have been observed for specific levels. The discrepancies suggest the need for further theoretical and experimental studies with other heavy ions along these isoelectronic sequences.
  Phys. Rev. A. 05/2006; 73(5).
• Article: Lifetime measurement of the Ar XIV 1s^2 2s^2 2p^2 P_ 3∕ 2^o metastable level at the Heidelberg electron-beam ion trap

  A. Lapierre, JRC López-Urrutia, J. Braun, G. Brenner
  Physical Review A. 01/2006;
• Article: Lifetime measurement of the Ar XIV 1s sup 2 2s sup 2 2p sup 2 P sub 3/2sup o metastable level at the Heidelberg electron-beam ion trap

  A. Lapierre, LU Crespo, J. Braun, G. Brenner
  Physical Review. A. 01/2006;
• Article: Lifetime measurement of the Ar XIV 1 s2 2 s2 2p P 3/2 o2 metastable level at the Heidelberg electron-beam ion trap

  A. Lapierre, J.R. Crespo López-Urrutia, J. Braun, G. Brenner, H. Bruhns, D. Fischer, A.J. González Martínez, V. Mironov, C. Osborne, G. Sikler, R. Soria Orts, H. Tawara, J. Ullrich, V.M. Shabaev, I.I. Tupitsyn, A. Volotka
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  ABSTRACT: Cited By (since 1996): 11, Export Date: 23 October 2011, Source: Scopus, Art. No.: 052507, CODEN: PLRAA, doi: 10.1103/PhysRevA.73.052507
  Physical Review A - Atomic, Molecular, and Optical Physics. 01/2006; 73.
• Article: Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s(2)2s(2)2p2p0(3/2) level in boronlike argon.

  A Lapierre, U D Jentschura, J R Crespo López-Urrutia, J Braun, G Brenner, H Bruhns, D Fischer, A J González Martínez, Z Harman, W R Johnson, C H Keitel, V Mironov, C J Osborne, G Sikler, R Soria Orts, V Shabaev, H Tawara, I I Tupitsyn, J Ullrich, A Volotka
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  ABSTRACT: The lifetime of the Ar13+ 1s(2)2s(2)2p2p0(3/2) metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately shorter than our experimental result.
  Physical Review Letters 11/2005; 95(18):183001. · 7.37 Impact Factor
• Article: State-selective quantum interference observed in the recombination of highly charged Hg 75+...78+ mercury ions in an electron beam ion trap.

  A J González Martínez, J R Crespo López-Urrutia, J Braun, G Brenner, H Bruhns, A Lapierre, V Mironov, R Soria Orts, H Tawara, M Trinczek, J Ullrich, J H Scofield
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  ABSTRACT: We present experimental data on the state-selective quantum interference between different pathways of photorecombination, namely, radiative and dielectronic recombination, in the KLL resonances of highly charged mercury ions. The interference, observed for well resolved electronic states in the Heidelberg electron beam ion trap, manifests itself in the asymmetry of line shapes, characterized by "Fano factors," which have been determined with unprecedented precision, as well as their excitation energies, for several strong dielectronic resonances.
  Physical Review Letters 06/2005; 94(20):203201. · 7.37 Impact Factor
• Article: Do Electrons and Ions Coexist in an EBIT?

  A. Lapierre, JRC Lopez-Urrutia, J. Braun
  Physics with Ultra Slow …. 01/2005;
• Article: Novel technique for high-precision Bragg-angle determination in crystal x-ray spectroscopy

  J. Braun, H. Bruhns, M. Trinczek
  Review of scientific …. 01/2005;
• Article: State-selective quantum interference observed in the recombination of highly charged Hg 75 + 78 + mercury ions in an electron beam ion trap

  A.J. González Martínez, J.R.C. López-Urrutia, J. Braun, G. Brenner, H. Bruhns, A. Lapierre, V. Mironov, R. Soria Orts, H. Tawara, M. Trinczek, J. Ullrich, J.H. Scofield
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  ABSTRACT: Cited By (since 1996): 34, Export Date: 23 October 2011, Source: Scopus, Art. No.: 203201, CODEN: PRLTA, doi: 10.1103/PhysRevLett.94.203201
  Physical Review Letters. 01/2005; 94.
• Article: High precision measurements of forbidden transitions in highly charged ions at the Heidelberg EBIT

  LU Crespo, A. Artemyev, J. Braun, G. Brenner
  Nuclear Instruments and …. 01/2005;
• Source

  Available from: Ilya Tupitsyn

  Article: Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s22s22pP3/2o2 level in boronlike argon

  A. Lapierre, U.D. Jentschura, J.R. Crespo López-Urrutia, J. Braun, G. Brenner, H. Bruhns, D. Fischer, A.J. González Martínez, Z. Harman, W.R. Johnson, C.H. Keitel, V. Mironov, C.J. Osborne, G. Sikler, R. Soria Orts, V. Shabaev, H. Tawara, I.I. Tupitsyn, J. Ullrich, A. Volotka
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  ABSTRACT: Cited By (since 1996): 32, Export Date: 23 October 2011, Source: Scopus, Art. No.: 183001, CODEN: PRLTA, doi: 10.1103/PhysRevLett.95.183001
  Physical Review Letters. 01/2005; 95:1-4.
• Article: Progress at the heidelberg ebit

  JR López-Urrutia, J. Braun, G. Brenner
  Journal of Physics: …. 01/2004;
• Article: Optimization of the charge state distribution of the ion beam extracted from an EBIT by dielectronic recombination

  JRC López-Urrutia, J. Braun, G. Brenner
  Review of scientific …. 01/2004;