Publications (28)61.7 Total impact
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ABSTRACT: The research program at the Heidelberg Electron Beam Ion Trap (EBIT) has concentrated mainly on precision measurements relevant to quantum electrodynamics (QED) and nuclear physics. Spectroscopic measurements in the optical region have delivered the most accurate wavelengths ever reported for highly charged ions, extracting even isotopic shifts. The forbidden transitions of Blike Ar XIV and Belike Ar XV ions were studied. They are especially interesting, since the QED contributions are as large as 0.2%. Improved atomic structure calculations allowed for the determination of their values with growing accuracy. The lifetimes of the corresponding metastable levels have also been measured with an uncertainty of less than 0.5% thus becoming sensitive to the influence of the bound electron anomalous magnetic moment, so far an almost experimentally unexplored QED effect. A new laser spectroscopic setup aims at facilitating future studies of the hyperfine structure of heavy hydrogenic ions. Through the study of the dielectronic recombination, information on rare processes, such as twoelectrononephoton transitions in Ar16+, or the interference effects between dielectronic and radiative recombination in Hg77+, and accurate values for the excitation energies of very heavy HCI have been obtained. A novel Xray crystal spectrometer allowing absolute Xray wavelength measurements in the range up to 15 keV with very high precision and reproducibility is currently used to study the Lyman series of Hlike ions of mediumZ ions and the 2s2p transitions of very heavy Lilike ions. PACS Nos.: 31.30.Jv, 32.80.Fb, 32.80.Dz, 32.30.Jv, 32.30.Rj, 95.30.DrCanadian Journal of Physics 02/2011; 83(4):387393. DOI:10.1139/p05015 · 0.96 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Singleelectron capture in 14 keV q(1) Ar15+...18++He collisions is investigated both experimentally and theoretically. Partial cross sections and projectile scattering angle dependencies have been deduced from the target ion recoil momenta measured by the COLTRIMS technique. The comparison with closecoupling results obtained from a twocentre extension of the basis generator method yields good overall agreement, demonstrating the applicability of closecoupling calculations to collision systems involving highly charged ions in charge states up to 18+.Journal of Physics B Atomic Molecular and Optical Physics 10/2008; 41(19). DOI:10.1088/09534075/41/19/195203 · 1.98 Impact Factor 
Article: Compact soft xray spectrometer for plasma diagnostics at the Heidelberg Electron Beam Ion Trap
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ABSTRACT: A compact flatfield soft xray grazingincidence grating spectrometer equipped with a cryogenically cooled backilluminated chargecoupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1 to 37 nm using two different gratings. In slitless operation mode, it directly images a radiation source, in this case ions confined in an electron beam ion trap, with high efficiency and reaching hereby a resolving power of lambda/Deltalambda approximately =130 at 2 nm and of lambda/Deltalambda approximately =600 at 28 nm. Capable of automatized operation, its low noise and excellent stability make it an ideal instrument not only for spectroscopic diagnostics requiring wide spectral coverage but also for precision wavelength measurements.Review of Scientific Instruments 01/2008; 78(12):123105. DOI:10.1063/1.2818808 · 1.61 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The Zeeman line components of the magneticdipole (M1) 1s{sup 2}2s{sup 2}2p {sup 2}P{sub 1/2}{sup 2}P{sub 3/2} transition in boronlike Ar{sup 13+} were experimentally resolved by highprecision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and firstexcited levels to be g{sub 1/2}=0.663(7) and g{sub 3/2}=1.333(2), respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound nonS state of a multielectron ion with a 1.5 partsperthousand accuracy. The results are compared to theoretical calculations by means of the configuration interaction DiracFockSturmian method including electron correlation effects and additional quantum electrodynamic corrections. Our measurements show that the classical Lande g factor formula is sufficiently accurate to the present level of accuracy in fewelectron ions of medium nuclear charge number Z.Physical Review A 11/2007; 76(5). · 2.81 Impact Factor 
Article: Zeeman splitting and g factor of the 1s(2)2s(2)2p (2)P(3/2) and (2)P(1/2) levels in Ar(13+)
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ABSTRACT: The Zeeman line components of the magneticdipole (M1) 1s(2)2s(2)2p (2)P(1/2)(2)P(3/2) transition in boronlike Ar(13+) were experimentally resolved by highprecision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and firstexcited levels to be g(1/2)=0.663(7) and g(3/2)=1.333(2), respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound nonS state of a multielectron ion with a 1.5 partsperthousand accuracy. The results are compared to theoretical calculations by means of the configuration interaction DiracFockSturmian method including electron correlation effects and additional quantum electrodynamic corrections. Our measurements show that the classical Lande g factor formula is sufficiently accurate to the present level of accuracy in fewelectron ions of medium nuclear charge number Z.Physical Review A 11/2007; 76(5). DOI:10.1103/PhysRevA.76.052501 · 2.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The Zeeman line components of the magneticdipole (M1) 1s22s22p P1/22 P3/22 transition in boronlike Ar13+ were experimentally resolved by highprecision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and firstexcited levels to be g1/2=0.663(7) and g3/2=1.333(2) , respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound non S state of a multielectron ion with a 1.5 partsperthousand accuracy. The results are compared to theoretical calculations by means of the configuration interaction DiracFockSturmian method including electron correlation effects and additional quantum electrodynamic corrections. Our measurements show that the classical Landé g factor formula is sufficiently accurate to the present level of accuracy in fewelectron ions of medium nuclear charge number Z .Physical Review A 11/2007; · 2.81 Impact Factor 
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ABSTRACT: Cited By (since 1996): 1, Export Date: 23 October 2011, Source: Scopus, Art. No.: 012001, doi: 10.1088/17426596/72/1/012001  [Show abstract] [Hide abstract]
ABSTRACT: Cited By (since 1996): 4, Export Date: 23 October 2011, Source: Scopus, Art. No.: 052501, CODEN: PLRAA, doi: 10.1103/PhysRevA.76.052501 
Article: Relativistic nuclear recoil, electron correlation and QED effects in highly charged Ar ions
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ABSTRACT: We have performed extensive theoretical studies on the 1s^22s^22p^2P3/2  ^2P1/2 M1 transition in Ar^13+ ions. Accurate radiative lifetimes are sensitive to QED corrections like the electron anomalous magnetic moment and to relativistic electron correlation effects. The lifetime of the P3/2 metastable state was determined to be 9.573(4)(5) ms (stat)(syst) [1] using the Heidelberg electron beam ion trap. Theoretical predictions cluster around a value that is significantly shorter than this highprecision experimental result. This discrepancy is presently unexplained. The wavelengths of the above transition in Ar^13+ and the 1s^22s2p ^3P1  ^3P2 M1 transition in Ar^14+ were compared for the isotopes ^36Ar and ^40Ar [2]. The observed mass shift has confirmed the relativistic theory of nuclear recoil effects in manybody systems. Our calculations, based on the fully relativistic recoil operator, are in excellent agreement with the measured results. [1] A. Lapierre, U.D. Jentschura, J.R. Crespo L'opezUrrutia et al., Phys. Rev. Lett. 95, 183001 (2005); [2] R. Soria Orts, Z. Harman, J.R. Crespo L'opezUrrutia et al., Phys. Rev. Lett. 97, 103002 (2006)  [Show abstract] [Hide abstract]
ABSTRACT: The relativistic recoil effect has been the object of experimental investigations using highly charged ions at the Heidelberg electron beam ion trap. Its scaling with the nuclear charge Z boosts its contribution to a measurable level in the magneticdipole (M1) transitions of B and Belike Ar ions. The isotope shifts of 36Ar versus 40Ar have been detected with subppm accuracy, and the recoil effect contribution was extracted from the 1s(2)2s(2)2p 2P(1/2)  2P(3/2) transition in Ar13+ and the 1s(2)2s2p 3P13P2 transition in Ar14+. The experimental isotope shifts of 0.00123(6) nm (Ar13+) and 0.00120(10) nm (Ar14+) are in agreement with our present predictions of 0.00123(5) nm (Ar13+) and 0.00122(5) nm (Ar14+) based on the total relativistic recoil operator, confirming that a thorough understanding of correlated relativistic electron dynamics is necessary even in a region of intermediate nuclear charges.Physical Review Letters 10/2006; 97(10):103002. DOI:10.1103/PhysRevLett.97.103002 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The photorecombination of highly charged fewelectron 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 stateselected 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 Helike Hg78+, a good agreement between the experimental results and the calculations has been found. However, for the capture into Li, Be, and Blike 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.Physical Review A 05/2006; 73(5). DOI:10.1103/PhysRevA.73.052710 · 2.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present the details of an accurate lifetime measurement of the 1s22s22pP3/2o2 metastable level in boronlike Ar XIV performed at the Heidelberg electron beam ion trap [A. Lapierre , Phys. Rev. Lett. 95, 183001 (2005)]. The lifetime was inferred from decay curves resulting from deexcitation of the metastable level to its P1/2o2 ground state through a magneticdipole (M1) transition upon cyclically turning on and off the electron beam. The measured lifetime of 9.573(4)((+12)/(5))ms (stat)(syst) is in disagreement with a trend of theoretical predictions of 9.53(1)ms , which include the effect of the electron anomalous magnetic moment. Systematic effects were investigated by studying with high statistical significance the dependence of the decay times of the curves on various trapping conditions. The asymptotic trend of the decay times observed for increasingly high trapping potentials, which indicates negligible ion losses within a ms time scale, is in agreement with a theoretical model describing the ion escape rate in electrostatic ion traps. However, for high trapping potentials, we observed an unexpected slowly decaying component suggesting the presence of trapped lowenergy electrons. Their origin, dynamics, and temperature, as well as their possible effects on the measured lifetime were investigated.Physical Review A 05/2006; 73(5). DOI:10.1103/PhysRevA.73.052507 · 2.81 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present the details of an accurate lifetime measurement of the 1sÂ²2sÂ²2p Â²Pââ{sup o} metastable level in boronlike Ar XIV performed at the Heidelberg electron beam ion trap [A. Lapierre et al., Phys. Rev. Lett. 95, 183001 (2005)]. The lifetime was inferred from decay curves resulting from deexcitation of the metastable level to its Â²Pââ{sup o} ground state through a magneticdipole (M1) transition upon cyclically turning on and off the electron beam. The measured lifetime of 9.573(4)((+12/5)) ms (stat)(syst) is in disagreement with a trend of theoretical predictions of 9.53(1) ms, which include the effect of the electron anomalous magnetic moment. Systematic effects were investigated by studying with high statistical significance the dependence of the decay times of the curves on various trapping conditions. The asymptotic trend of the decay times observed for increasingly high trapping potentials, which indicates negligible ion losses within a ms time scale, is in agreement with a theoretical model describing the ion escape rate in electrostatic ion traps. However, for high trapping potentials, we observed an unexpected slowly decaying component suggesting the presence of trapped lowenergy electrons. Their origin, dynamics, and temperature, as well as their possible effects on the measured lifetime were investigated. 
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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  [Show abstract] [Hide abstract]
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 electronelectron correlation effects like the frequencydependent 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. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The lifetime of the Ar13+ 1s(2)2s(2)2p P2(3/2)o metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5) ms(stat)(syst). 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 electronelectron correlation effects like the frequencydependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately 3 sigma shorter than our experimental result.Physical Review Letters 10/2005; 95(18):14. DOI:10.1103/PhysRevLett.95.183001 · 7.51 Impact Factor 
Article: High precision measurements of forbidden transitions in highly charged ions at the Heidelberg EBIT
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ABSTRACT: Fewelectron ions, which can be produced and studied at rest in electron beam ion traps (EBITs) are very well suited for the study of nuclear size effects and QED in strong fields, but the various contributions are usually entangled. Therefore, combinations of experiments with ions in different charge states are required to separate those contributions. In order to achieve this, several spectroscopic techniques have been recently implemented at the Heidelberg EBIT, aiming at high resolution and accuracy. In the optical region the most accurate wavelengths ever reported for highly charged ions [Draganić et al., Phys. Rev. Lett. 91 (2003) 183001] have been obtained, the results being sensitive to isotopic shifts [Tupitsyn et al., Phys. Rev. A 68 (2003) 022511] at the 0.01 meV level. The forbidden transitions of Blike ArXIV and Belike ArXV ions studied here are especially interesting, since the QED contributions are as large as 0.2%. Improved atomic structure calculations allow to determine their values with growing accuracy, although the theoretical accuracy still lags three to four orders of magnitude behind the experimental one. In a different experiment, the lifetime of the corresponding metastable level has also been measured with an uncertainty of less than 0.2% thus becoming sensitive to the influence of the bound electron anomalous magnetic moment, an almost experimentally unexplored QED effect so far. A new laser spectroscopic setup aims at facilitating future studies of the hyperfine structure of heavy hydrogenic ions. Through the study of the dielectronic recombination, information on rare processes, such as twoelectron–onephoton transitions in Ar16+ [Zou et al., Phys. Rev. A 67 (2003) 42703] at energies of around 2 keV, or the interference effects between dielectronic and radiative recombination in Hg77+ at 50 keV, and accurate values for the excitation energies of very heavy HCI have been obtained. A novel Xray crystal spectrometer allowing absolute Xray wavelength measurements in the range up to 15 keV with very high precision and reproducibility is currently used to study the Lyman series of Hlike ions of mediumZ ions and the 2s–2p transitions of very heavy Lilike ions.Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/2005; 235(14235):8591. DOI:10.1016/j.nimb.2005.03.151 · 1.12 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present experimental data on the stateselective 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 05/2005; 94(20). DOI:10.1103/PhysRevLett.94.203201 · 7.51 Impact Factor
Publication Stats
313  Citations  
61.70  Total Impact Points  
Top Journals
Institutions

2003–2007

Max Planck Institute for Nuclear Physics
Heidelburg, BadenWürttemberg, Germany 
Universität Kassel
Cassel, Hesse, Germany


2006

Saint Petersburg State University
 Institute of Radiophysics
SanktPeterburg, St.Petersburg, Russia


2005

University of California, Berkeley
 Department of Physics
Berkeley, MO, United States
