Publications (47)44.06 Total impact
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Article: Detection system for forward emitted photons at the Experimental Storage Ring at GSI
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ABSTRACT: A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the beam position. The new detection system has been used in the LIBELLE experiment at ESR and enabled for the first time the detection of the ground-state hyperfine M1 transition in lithium-like bismuth (209Bi80+) in a laser-spectroscopy measurement.05/2013; -
Article: Progress of ultra trace determination of technetium using laser resonance ionization mass spectrometry.
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ABSTRACT: Laser resonance ionization mass spectrometry (RIMS) represents one of the most sensitive and selective techniques for ultra trace determination of long-lived radioisotopes. The isotope (99g)Tc constitutes a specific candidate of high relevance concerning its environmental behavior as well as fundamental research applications. Based on the recent precision determination of the ionization potential of technetium by laser resonance ionization, refined resonant optical excitation pathways have been derived for analytical determination of ultra trace amounts of (99g)Tc by laser mass spectrometric approaches. The state of the art and the specifications of RIMS-based ultra trace determination for (99g)Tc, leading to a level of detection of ε ≈ 3 × 10( -4) atoms (3 μBq), are reported.Analytical and Bioanalytical Chemistry 08/2012; 404(8):2173-6. · 3.78 Impact Factor -
Article: Experimental test of special relativity by laser spectroscopy
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ABSTRACT: The Doppler-free laser-spectroscopic frequency measurement of Doppler-shifted optical lines in forward and backward direction of a fast ion beam permits a sensitive test of the relativistic Doppler-formula and, hence, the relativistic time dilation factor gSR = ( 1 - n2 \mathord/ \vphantom n2 c2 c2 ) - 1 \mathord/ \vphantom - 1 2 2 \gamma _{{SR}} = {\left( {1 - {\nu ^{2} } \mathord{\left/ {\vphantom {{\nu ^{2} } {c^{2} }}} \right. } {c^{2} }} \right)}^{{{ - 1} \mathord{\left/ {\vphantom {{ - 1} 2}} \right. } 2}} . An experiment on metastable 7Li+, stored at a velocity of v = 0.064c in the Heidelberg heavy-ion storage ring TSR, has confirmed time dilation with unprecedented accuracy. Latest tests at two different ion-velocities (v = 0.03c and v = 0.064c) will enhance these measurements. An improved version of this experiment will be carried out at the experimental storage ring (ESR) at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. The ESR permits 7Li+ to be stored at v = 0.33c which promises an improvement of the sensitivity to deviations from γ SR by an order of magnitude. A first test at the ESR has shown the feasibility for this kind of experiment.Hyperfine Interactions 04/2012; 171(1):57-67. · 0.21 Impact Factor -
Article: Comment on: “Lorentz violation in high-energy ions” by Santosh Devasia
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ABSTRACT: In an article “Lorentz violation in high-energy ions” by S. Devasia published in this Journal [EPJ C 69, 343 (2010)], our recent Doppler shift experiments on fast ion beams are reanalyzed. Contrary to our analysis, Devasia concludes that our results provide an “indication of Lorentz violation”. We argue that this conclusion is based on a fundamental misunderstanding of our experimental scheme and reiterate that our results are in excellent agreement with Special Relativity.European Physical Journal C 04/2012; 71(3):1-2. · 3.63 Impact Factor -
Article: Comment on "Missing Transverse-Doppler Effect in Time-Dilation Experiments with High-Speed Ions"
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ABSTRACT: In an article "Missing Transverse-Doppler Effect in Time-Dilation Experiments with High-Speed Ions" by S. Devasia [arXiv:1003.2970v1], our recent Doppler shift experiments on fast ion beams are reanalyzed. Contrary to our analysis, Devasia concludes that our results provide an "indication of Lorentz violation". We argue that this conclusion is based on a fundamental misunderstanding of our experimental scheme and reiterate that our results are in excellent agreement with Special Relativity.02/2011; -
Article: Discovery of a long-lived low-lying isomeric state in 80Ga
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ABSTRACT: Collinear laser spectroscopy was performed on the 80Ga isotope at ISOLDE, CERN. A low-lying isomeric state with a half-life much greater than 200 ms was discovered. The nuclear spins and moments of the ground and isomeric states and the isomer shift are discussed. Probable spins and parities are assigned to both long-lived states (3- and 6-) deduced from a comparison of the measured moments to shell-model calculations.Physical Review C 11/2010; 82(1-5):051302. · 3.31 Impact Factor -
Article: Nuclear spins and moments of Ga isotopes reveal sudden structural changes between N=40 and N=50.
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ABSTRACT: Collinear laser spectroscopy was performed on Ga (Z=31) isotopes at ISOLDE, CERN. A gas-filled linear Paul trap (ISCOOL) was used to extend measurements towards very neutron-rich isotopes (N=36-50). A ground state (g.s.) spin I=1/2 is measured for 73Ga, being near degenerate with a 3/2{-} isomer (75 eV≲E{ex}≲1 keV). The 79Ga g.s., with I=3/2, is dominated by protons in the πf{5/2} orbital and in 81Ga the 5/2{-} level becomes the g.s. The data are compared to shell-model calculations in the f{5/2}pg{9/2} model space, calling for further theoretical developments and new experiments.Physical Review Letters 06/2010; 104(25):252502. · 7.37 Impact Factor -
Article: MATS and LaSpec: High-precision experiments using ion traps and lasers at FAIR
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ABSTRACT: Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique “fingerprint”. Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10−5 to below 10−8 for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an A_dvanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10−9 can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e.g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility.Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner.The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with β-delayed neutron detection) has been achieved with rates of only a few atoms per second.This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively.The European Physical Journal Special Topics 05/2010; 183:1. · 1.56 Impact Factor -
Article: An ion cooler-buncher for high-sensitivity collinear laser spectroscopy at ISOLDE
European Physical Journal A 01/2009; 42(3):503-507. · 2.19 Impact Factor -
Article: Labeling the human skeleton with 41Ca to assess changes in bone calcium metabolism.
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ABSTRACT: Bone research is limited by the methods available for detecting changes in bone metabolism. While dual X-ray absorptiometry is rather insensitive, biochemical markers are subject to significant intra-individual variation. In the study presented here, we evaluated the isotopic labeling of bone using 41Ca, a long-lived radiotracer, as an alternative approach. After successful labeling of the skeleton, changes in the systematics of urinary 41Ca excretion are expected to directly reflect changes in bone Ca metabolism. A minute amount of 41Ca (100 nCi) was administered orally to 22 postmenopausal women. Kinetics of tracer excretion were assessed by monitoring changes in urinary 41Ca/40Ca isotope ratios up to 700 days post-dosing using accelerator mass spectrometry and resonance ionization mass spectrometry. Isotopic labeling of the skeleton was evaluated by two different approaches: (i) urinary 41Ca data were fitted to an established function consisting of an exponential term and a power law term for each individual; (ii) 41Ca data were analyzed by population pharmacokinetic (NONMEM) analysis to identify a compartmental model that describes urinary 41Ca tracer kinetics. A linear three-compartment model with a central compartment and two sequential peripheral compartments was found to best fit the 41Ca data. Fits based on the use of the combined exponential/power law function describing urinary tracer excretion showed substantially higher deviations between predicted and measured values than fits based on the compartmental modeling approach. By establishing the urinary 41Ca excretion pattern using data points up to day 500 and extrapolating these curves up to day 700, it was found that the calculated 41Ca/40Ca isotope ratios in urine were significantly lower than the observed 41Ca/40Ca isotope ratios for both techniques. Compartmental analysis can overcome this limitation. By identifying relative changes in transfer rates between compartments in response to an intervention, inaccuracies in the underlying model cancel out. Changes in tracer distribution between compartments were modeled based on identified kinetic parameters. While changes in bone formation and resorption can, in principle, be assessed by monitoring urinary 41Ca excretion over the first few weeks post-dosing, assessment of an intervention effect is more reliable approximately 150 days post-dosing when excreted tracer originates mainly from bone.Analytical and Bioanalytical Chemistry 12/2006; 386(6):1587-602. · 3.78 Impact Factor -
Article: Precision branching ratio measurement for the superallowed beta+ emitter 62Ga and isospin-symmetry-breaking corrections in A>or=62 nuclei.
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ABSTRACT: A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta+ decay of 62Ga were identified, establishing the dominant superallowed branching ratio to be (99.861+/-0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6+/-1.4 s for 62Ga decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A>or=62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays.Physical Review Letters 09/2006; 97(10):102501. · 7.37 Impact Factor -
Chapter: Development Towards a Laser Ion Source Trap for the Production of Exotic Species
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ABSTRACT: A new type of resonance ionization laser ion source (RILIS) is presently being developed and tested at the off-line mass separator at Mainz University for future use at on-line exotic rare isotopes production facilities. For highest isobaric selectivity, this RILIS approach decouples the evaporation and ionization process. A further advantage is the generation of full temporal control of the resulting high quality ion beam. These facts are realized by a combination of atomizer — ion repeller — ion cooler and trap, which is operated together with a state-of-the-art, all solid state laser system. The principle and performance of this laser ion source trap (LIST) system are discussed applying simulation studies for the repeller-trap combination and first measurements for characterization.08/2006: pages 29-38; -
Article: High-resolution γ-ray spectroscopy: a versatile tool for nuclear β-decay studies at TRIUMF-ISAC
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ABSTRACT: High-resolution γ-ray spectroscopy is essential to fully exploit the unique, high-quality beams available at the next generation of radioactive ion beam facilities such as the TRIUMF isotope separator and accelerator (ISAC). The 8π spectrometer, which consists of 20 Compton-suppressed HPGe detectors, has recently been reconfigured for a vigorous research programme in weak interaction and nuclear structure physics. With the addition of a variety of ancillary detectors it has become the world's most powerful device dedicated to β-decay studies. This paper provides a brief overview of the apparatus and highlights from recent experiments.Journal of Physics G Nuclear and Particle Physics 09/2005; 31(10):S1491. · 4.18 Impact Factor -
Article: Trace determination of gadolinium in biomedical samples by diode laser-based multi-step resonance ionization mass spectrometry.
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ABSTRACT: The application of high-resolution multi-step resonance ionization mass spectrometry (RIMS) to the trace determination of the rare earth element gadolinium is described. Utilizing three-step resonant excitation into an autoionizing level, both isobaric and isotopic selectivity of >10(7) were attained. An overall detection efficiency of approximately 10(-7) and an isotope specific detection limit of 1.5 x 10(9) atoms have been demonstrated. When targeting the major isotope (158)Gd, this corresponds to a total Gd detection limit of 1.6 pg. Additionally, linear response has been demonstrated over a dynamic range of six orders of magnitude. The method has been used to determine the Gd content in various normal and tumor tissue samples, taken from a laboratory mouse shortly after injection of gadolinium diethylenetriaminepentaacetic acid dimeglumine (Gd-DTPA), which is used as a contrast agent for magnetic resonance imaging (MRI). The RIMS results show Gd concentrations that vary by more than two orders of magnitude (0.07-11.5 microg mL(-1)) depending on the tissue type. This variability is similar to that observed in MRI scans that depict Gd-DTPA content in the mouse prior to dissection, and illustrates the potential for quantitative trace analysis in microsamples of biomedical materials.Analytical and Bioanalytical Chemistry 04/2002; 372(7-8):759-65. · 3.78 Impact Factor -
Article: 41Ca ultratrace determination with isotopic selectivity > 10(12) by diode-laser-based RIMS.
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ABSTRACT: 41Ca ultratrace determination by diode-laser-based resonance ionization mass spectrometry with extremely high isotopic selectivity is presented. Application to environmental dosimetry of nuclear reactor components, to cosmochemical investigations of production cross sections, and biomedical isotope-tracer studies of human calcium kinetics are discussed. Future investigations are possible use in 41Ca-radiodating. Depending on the application, 41Ca isotopic abundances in the range of 10(-9) to 10(-15) relative to the dominant stable isotope 40Ca must be determined. Either double- or triple-resonance optical excitation with narrow-band extended cavity diode lasers and subsequent non-resonant photoionization of calcium in a collimated atomic beam were used. The resulting photoions are detected with a quadrupole mass spectrometer optimized for background reduction and neighboring mass suppression. Applying the full triple-resonance scheme provides a selectivity of approximately 5 x 10(12) in the suppression of neighboring isotopes and > 10(8) for isobars, together with an overall detection efficiency of approximately 5 x 10(-5). Measurements on a variety of sample types are discussed; the accuracy and reproducibility of the resulting 41Ca/40Ca isotope ratios was better than 5%.Fresenius Journal of Analytical Chemistry 07/2001; 370(5):508-12. -
Article: Selective ultratrace analysis of 41Ca by laser resonance ionization
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ABSTRACT: A compact resonance ionization mass spectrometer is presented. It is presently applied for sensitive and highly selective ultratrace determination of the long-lived radioisotope 41Ca for environmental, biological, and fundamental investigations. The development of coherent multistep resonance ionization enables the realization of experimental detection limits as low as106 atoms per sample and very high isotopic selectivity above 1012.Hyperfine Interactions 07/2000; 127(1):519-522. · 0.21 Impact Factor -
Article: Sub-Doppler laser spectroscopy on relativistic beams and tests of Lorentz invariance
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ABSTRACT: We demonstrate sub-Doppler laser spectroscopy with a beam of 7Li+ ions stored at 33.8% of the speed of light in the experimental storage ring at GSI. Using two lasers, the one copropagating and the other counterpropagating, with respect to the ion beam, a fluorescence line is observed via optical-optical double-resonance spectroscopy on a Λ-type level configuration. A linewidth of ≈114 MHz is found, which is 12 times narrower than the Doppler broadening due to the momentum spread of the ion beam. Interpreted as a test of Lorentz invariance, we find |α̂2|<1.2×10−5, a 25× tighter limit on O((v/c)4) deviations from time dilation than any other experiment.Phys. Rev. A. 80(2). -
Article: Towards a precision test of time dilation at high velocity
Canadian Journal of Physics. 87(7):749-756. -
Article: Preparatory measurements for a test of time dilation in the ESR
Canadian Journal of Physics. 89(1):85-93. -
Article: Sub-Doppler laser spectroscopy on relativistic beams and tests of Lorentz invariance
Physical Review A. 80(2).
Top co-authors
Top Journals
Institutions
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2010–2012
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GSI Helmholtzzentrum für Schwerionenforschung
Jena, Thuringia, Germany
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2000–2006
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Johannes Gutenberg-Universität Mainz
- Institute of Physics
Mainz, Rhineland-Palatinate, Germany
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