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Publikationen von
Dr. Alexandre Gumberidze

Alle Publikationen des HI Jena

2022

B. Zhu, A. Gumberidze, T. Over, G. Weber, Z. Andelkovic, A. Bräuning-Demian, R. J. Chen, D. Dmytriiev, O. Forstner, C. Hahn, F. Herfurth, M. O. Herdrich, P.-M. Hillenbrand, A. Kalinin, F. M. Kröger, M. Lestinsky, Yu. A. Litvinov, E. B. Menz, W. Middents, T. Morgenroth, N. Petridis, Ph. Pfäfflein, M. S. Sanjari, R. S. Sidhu, U. Spillmann, R. Schuch, S. Schippers, S. Trotsenko, L. Varga, G. Vorobyev, and Th. Stöhlker
X-ray emission associated with radiative recombination for Pb⁸²⁺ ions at threshold energies
Physical Review A 105, 052804 (2022)

Abstract: For decelerated bare lead ions at a low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at threshold energies has been studied at the electron cooler of CRYRING@ESR at GSI, Darmstadt. In our experiment, we observed the full x-ray emission pattern by utilizing dedicated x-ray detection chambers installed at 0∘ and 180∘ observation geometry. Most remarkably, no line distortion effects due to delayed emission are present in the well-defined x-ray spectra, spanning a wide range of x-ray energies (from about 5 to 100 keV), which enables us to identify fine-structure resolved Lyman, Balmer, and Paschen x-ray lines along with the RR transitions into the K, L, and M shells of the ions. For comparison with theory, an elaborate theoretical model is established taking into account the initial population distribution via RR for all atomic levels up to Rydberg states with principal quantum number n=165 in combination with time-dependent feeding transitions. Within the statistical accuracy, the experimental data are in very good agreement with the results of rigorous relativistic predictions. Most notably, this comparison sheds light on the contribution of prompt and delayed x-ray emission (up to 70 ns) to the observed x-ray spectra, originating in particular from yrast transitions into inner shells.

P.-M. Hillenbrand, S. Hagmann, Y. S. Kozhedub, E. P. Benis, C. Brandau, R. J. Chen, D. Dmytriiev, O. Forstner, J. Glorius, R. E. Grisenti, A. Gumberidze, M. Lestinsky, Yu. A. Litvinov, E. B. Menz, T. Morgenroth, S. Nanos, N. Petridis, Ph. Pfäfflein, H. Rothard, M. S. Sanjari, R. S. Sidhu, U. Spillmann, S. Trotsenko, I. I. Tupitsyn, L. Varga, and Th. Stöhlker
Single and double K-shell vacancy production in slow Xe⁵⁴⁺,⁵³⁺-Xe collisions
Physical Review A 105, 022810 (2022)

Abstract: We present an experimental and theoretical study of symmetric Xe54++Xe collisions at 50, 30, and 15 MeV/u, corresponding to strong perturbations with vK/vp=1.20, 1.55, and 2.20, respectively (vK is the classical K-shell orbital velocity and vp is the projectile velocity), as well as Xe53++Xe collisions at 15 MeV/u. For each of these systems, x-ray spectra are measured under a forward angle of 35∘ with respect to the projectile beam. Target satellite and hypersatellite radiation Kαs2,1 and Kαhs2,1, respectively, are analyzed and used to derive cross-section ratios for double-to-single target K-shell vacancy production. We compare our experimental results to relativistic time-dependent two-center calculations.

2021

P.-M. Hillenbrand, K. N. Lyashchenko, S. Hagmann, O. Andreev, D. Banas, E. P. Benis, I. Bondarev, C. Brandau, E. De Filippo, O. Forstner, J. Glorius, R. E. Grisenti, A. Gumberidze, D. L. Guo, M. O. Herdrich, M. Lestinsky, Y. Litvinov, V. Pagano, N. Petridis, M. S. Sanjari, D. Schury, U. Spillmann, S. Trotsenko, M. Vockert, A. B. Voitkiv, G. Weber, and T. Stoehlker
Electron-loss-to-continuum cusp in collisions of U89+ with N-2 and Xe
Physical Review A 104, 012809 (2021)

Abstract: We study the electron-loss-to-continuum (ELC) cusp experimentally and theoretically by comparing the ionization of U89+ projectiles in collisions with N-2 and Xe targets, at a beam energy of 75.91 MeV/u. The coincidence measurement between the singly ionized projectile and the energy of the emitted electron is used to compare the shape of the ELC cusp at weak and strong perturbations. A significant energy shift for the centroid of the electron cusp is observed for the heavy target of Xe as compared to the light target of N-2. Our results provide a stringent test for fully relativistic calculations of double-differential cross sections performed in the first-order approximation and in the continuum-distorted-wave approach.

A. Gumberidze, D. Thorn, A. Surzhykov, C. Fontes, D. Banas, H. Beyer, W. Chen, R. Grisenti, S. Hagmann, R. Hess, P.-M. Hillenbrand, P. Indelicato, C. Kozhuharov, M. Lestinsky, R. Märtin, N. Petridis, R. Popov, R. Schuch, U. Spillmann, S. Tashenov, S. Trotsenko, A. Warczak, G. Weber, W. Wen, D. Winters, N. Winters, Z. Yin, and T. Stöhlker
Angular Distribution of Characteristic Radiation Following the Excitation of He-Like Uranium in Relativistic Collisions
Atoms 9, 20 (2021)

Abstract: In this paper, we present an experimental and theoretical study of excitation processes for the heaviest stable helium-like ion, that is, He-like uranium occurring in relativistic collisions with hydrogen and argon targets. In particular, we concentrate on angular distributions of the characteristic K alpha radiation following the K -> L excitation of He-like uranium. We pay special attention to the magnetic sub-level population of the excited 1s2l(j) states, which is directly related to the angular distribution of the characteristic K alpha radiation. We show that the experimental data can be well described by calculations taking into account the excitation by the target nucleus as well as by the target electrons. Moreover, we demonstrate for the first time an important influence of the electron-impact excitation process on the angular distributions of the K alpha radiation produced by excitation of He-like uranium in collisions with different targets.

2020

P. Jagodziłski, D. Banaś, M. Pajek, A. Warczak, H. Beyer, A. Gumberidze, G. Weber, Th. Stöhlker, and M. Trassinelli
Concept and simulations of a high-resolution asymmetric von Hamos X-ray spectrometer for CRYRING@ESR electron cooler
Journal of Physics: Conference Series 1412, 132031 (2020)

Abstract: A concept of a high resolution asymmetric von Hamos X-ray spectrometer for the CRYRING@ESR electron cooler is described and its characteristics obtained by ray-tracing Monte-Carlo simulations are presented. The spectrometer will be used to study the QED e-ects in H-like medium-Z ions by measuring the energies of X-rays from radiative recombination of highly charged ions with cooling electrons, with a ppm precision of energy determination.

A. Gumberidze, C. Kozhuharov, R. Zhang, S. Trotsenko, Y. Kozhedub, R. Du, H. Bois, F. Beyer, K.-H. Blumenhagen, C. Brandau, A. Bräuning-Demian, W. Chen, O. Forstner, B. Gao, T. Gassner, R. Grisenti, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, A. Kumar, M. Lestinsky, Y. Litvinov, N. Petridis, D. Schury, U. Spillmann, C. Trageser, M. Trassinelli, X. Tu, and T. Stöhlker
Impact parameter sensitive study of inner-shell atomic processes in Xe54+, Xe52+ → Xe collisions
Journal of Physics: Conference Series 1412, 142015 (2020)

Abstract: In this work, we present a pilot experiment in the experimental storage ring (ESR) at GSI devoted to impact parameter sensitive studies of inner shell atomic processes for bare and He-like xenon ions (Xe54+, Xe52+) colliding with neutral xenon gas atoms. The projectile and target x-rays have been measured at different observation angles for all impact parameters as well as for the impact parameter range of ∼35 - 70 fm.

D. Schury, A. Méry, J. Ramillon, L. Adoui, J.-Y. Chesnel, A. Lévy, S. Macé, C. Prigent, J. Rangama, P. Rousseau, S. Steydli, M. Trassinelli, D. Vernhet, A. Gumberidze, T. Stöhlker, A. Bruning-Demian, C. Hahn, U. Spillmann, and E. Lamour
The low energy beamline of the FISIC experiment: Current status of construction and performance
Journal of Physics: Conference Series 1412, 162011 (2020)

Abstract: Ion-ion collisions between slow (kev/u) and fast (MeV/u) ions play an important role in for example astrophysical or inertial fusion plasmas as well as in ion-matter interaction. In this regime the energy transfer is maximum, as all primary electronic processes reach their maximum. At the same time up to today no reliable experimental data exists while being difficult to treat accurately by theory. We present the current status and performance of the low energy beam-line of the FISIC experiment which aims at filling in the blanks in this regime.

Y. Xing, J. Glorius, L. Varga, L. Bott, C. Brandau, B. Brückner, R. Chen, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, G. Gyürky, M. Heil, R. Hess, R. Hensch, P. Hillmann, P.-M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch, A. Khodaparast, T. Kisselbach, N. Klapper, C. Kozhuharov, D. Kurtulgil, G. Lane, C. Langer, C. Lederer-Woods, M. Lestinsky, S. Litvinov, Y. Litvinov, B. Löher, N. Petridis, U. Popp, M. Reed, R. Reifarth, M. Sanjari, H. Simon, Z. Slavkovská, U. Spillmann, M. Steck, T. Stöhlker, J. Stumm, T. Szücs, T. Nguyen, A. Zadeh, B. Thomas, S. Torilov, H. Törnqvist, C. Trageser, S. Trotsenko, M. Volknandt, M. Wang, M. Weigand, C. Wolf, P. Woods, Y. Zhang, and X. Zhou
Determination of luminosity for in-ring reactions: A new approach for the low-energy domain
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 982, 164367 (2020)

Abstract: Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results are in good agreement with an independent measurement based on the x-ray normalization method. Our new method provides an alternative way to precisely measure the luminosity in low-energy stored-beam configurations. This can be of great value in particular in dedicated low-energy storage rings where established methods are difficult or impossible to apply.

F. M. Kröger, G. Weber, M. O. Herdrich, J. Glorius, C. Langer, Z. Slavkovská, L. Bott, C. Brandau, B. Brückner, K. Blaum, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, Gy. Gyürky, S. Hagmann, C. Hahn, M. Heil, R. Hess, R. Hensch, P. Hillmann, P.-M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch, A. Khodaparast, T. Kisselbach, N. Klapper, C. Kozhuharov, D. Kurtulgil, G. Lane, C. Lederer-Woods, M. Lestinsky, S. Litvinov, Yu. A. Litvinov, B. Löher, F. Nolden, N. Petridis, U. Popp, M. Reed, R. Reifarth, M. S. Sanjari, H. Simon, U. Spillmann, M. Steck, J. Stumm, T. Szücs, T. T. Nguyen, A. T. Zadeh, B. Thomas, S. Yu. Torilov, H. Törnqvist, C. Trageser, S. Trotsenko, M. Volknandt, M. Weigand, C. Wolf, P. J. Woods, V. P. Shevelko, I. Yu. Tolstikhina, and Th. Stöhlker
Electron capture of Xe54+ in collisions with H2 molecules in the energy range between 5.5 and 30.9 MeV/u
Physical Review A 102, 042825 (2020)

Abstract: The electron-capture process was studied for Xe54+ colliding with H2 molecules at the internal gas target of the Experimental Storage Ring (ESR) at GSI, Darmstadt. Cross-section values for electron capture into excited projectile states were deduced from the observed emission cross section of Lyman radiation, being emitted by the hydrogenlike ions subsequent to the capture of a target electron. The ion beam energy range was varied between 5.5 and 30.9 MeV/u by applying the deceleration mode of the ESR. Thus, electron-capture data were recorded at the intermediate and, in particular, the low-collision-energy regime, well below the beam energy necessary to produce bare xenon ions. The obtained data are found to be in reasonable qualitative agreement with theoretical approaches, while a commonly applied empirical formula significantly overestimates the experimental findings.

P.-M. Hillenbrand, S. Hagmann, M. Groshev, D. Banaś, E. Benis, C. Brandau, E. De Filippo, O. Forstner, J. Glorius, R. Grisenti, A. Gumberidze, D. Guo, B. Hai, M. Herdrich, M. Lestinsky, Y. Litvinov, E. Pagano, N. Petridis, M. Sanjari, D. Schury, U. Spillmann, S. Trotsenko, M. Vockert, G. Weber, V. Yerokhin, and Th. Stöhlker
Radiative electron capture to the continuum in U89+ + N2 collisions: Experiment and theory
Physical Review A 101, 022708 (2020)

Abstract: For U89+ projectiles colliding at a beam energy of 75.91 MeV/u with a N2 target, we present a coincidence measurement between the cusp electrons emitted under an angle of 0° with respect to the projectile beam and the photons emitted under a polar angle of 90°. This radiative-electron-capture-to-continuum cusp directly probes the theory of electron-nucleus bremsstrahlung up to the high-energy endpoint in inverse kinematics. In the present study, significant improvement with respect to the experimental accuracy has been achieved, resulting in a finer agreement between experimental and theoretical results.

G. Weber, A. Gumberidze, M. Herdrich, R. Märtin, U. Spillmann, A. Surzhykov, D. Thorn, S. Trotsenko, N. Petridis, C. Fontes, and Th. Stöhlker
Towards a determination of absolute cross sections for projectile excitation of hydrogen‐like uranium in collisions with neutral atoms
X-Ray Spectrometry 49, 239 (2020)

Abstract: Recently, the contribution of the generalized Breit interaction to electron impact ionization was identified for the first time in a high‐Z system, namely, hydrogen‐like uranium. This study employed a measurement of the relative population of the j = 1/2 and j = 3/2 states of the L shell by projectile excitation in collision of U91+ with hydrogen and nitrogen targets. However, for a rigorous test of ion–atom collision theory, also the absolute excitation cross sections are of great importance. In the present work, we report on our efforts to extend the previous study to a determination of the absolute projectile excitation cross sections by normalization to the well‐known radiative electron capture process.

T. Gassner, A. Gumberidze, M. Trassinelli, R. Heß, U. Spillmann, D. Banaś, K.-H. Blumenhagen, F. Bosch, C. Brandau, W. Chen, C. Dimopoulou, E. Förster, R. Grisenti, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, P. Jagodzinski, T. Kämpfer, M. Lestinsky, D. Liesen, Y. Litvinov, R. Lötzsch, B. Manil, R. Märtin, F. Nolden, N. Petridis, M. Sanjari, K. Schulze, M. Schwemlein, A. Simionovici, M. Steck, Th. Stöhlker, C. Szabo, S. Trotsenko, I. Uschmann, G. Weber, O. Wehrhan, N. Winckler, D. Winters, N. Winters, E. Ziegler, and H. Beyer
High-resolution wavelength-dispersive spectroscopy of K-shell transitions in hydrogen-like gold
X-Ray Spectrometry 49, 204 (2020)

Abstract: We present a measurement of K‐shell transitions in H‐like gold (Au78+) using specially developed transmission type crystal spectrometers combined with Ge(i) microstrip detectors. The experiment has been carried out at the Experimental Storage Ring at GSI in Darmstadt. This is a first high‐resolution wavelength‐dispersive measurement of a K‐shell transition in a high‐Z H‐like ion, thus representing an important milestone in this field. Ideas on possible future improvements are discussed as well.

2019

F. Ozturk, B. Akkus, D. Atanasov, H. Beyer, F. Bosch, D. Boutin, C. Brandau, P. Bühler, R. Cakirli, R. Chen, W. Chen, X. Chen, I. Dillmann, C. Dimopoulou, W. Enders, H. Essel, T. Faestermann, O. Forstner, B. Gao, H. Geissel, R. Gernhäuser, R. Grisenti, A. Gumberidze, S. Hagmann, T. Heftrich, M. Heil, M. Herdrich, P.-M. Hillenbrand, T. Izumikawa, P. Kienle, C. Klaushofer, C. Kleffner, C. Kozhuharov, R. Knöbel, O. Kovalenko, S. Kreim, T. Kühl, C. Lederer-Woods, M. Lestinsky, S. Litvinov, Y. Litvinov, Z. Liu, X. Ma, L. Maier, B. Mei, H. Miura, I. Mukha, A. Najafi, D. Nagae, T. Nishimura, C. Nociforo, F. Nolden, T. Ohtsubo, Y. Oktem, S. Omika, A. Ozawa, N. Petridis, J. Piotrowski, R. Reifarth, J. Rossbach, R. Sánchez, M. Sanjari, C. Scheidenberger, R. Sidhu, H. Simon, U. Spillmann, M. Steck, Th. Stöhlker, B. Sun, L. Susam, F. Suzaki, T. Suzuki, S. Torilov, C. Trageser, M. Trassinelli, S. Trotsenko, X. Tu, P. Walker, M. Wang, G. Weber, H. Weick, N. Winckler, D. Winters, P. Woods, T. Yamaguchi, X. Xu, X. Yan, J. Yang, Y. Yuan, Y. Zhang, and X. Zhou
New test of modulated electron capture decay of hydrogen-like ¹⁴²Pm ions: Precision measurement of purely exponential decay
Physics Letters B 797, 134800 (2019)

Abstract: An experiment addressing electron capture (EC) decay of hydrogen-like ¹⁴²Pm⁶⁰⁺ ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126(7) s⁻¹ for automatic analysis and 0.0141(7) s⁻¹ for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4).

M. Vockert, G. Weber, H. Bräuning, A. Surzhykov, C. Brandau, S. Fritzsche, S. Geyer, S. Hagmann, S. Hess, C. Kozhuharov, R. Märtin, N. Petridis, R. Hess, S. Trotsenko, Yu. A. Litvinov, J. Glorius, A. Gumberidze, M. Steck, S. Litvinov, T. Gassner, P.-M. Hillenbrand, M. Lestinsky, F. Nolden, M. S. Sanjari, U. Popp, C. Trageser, D. F. A. Winters, U. Spillmann, T. Krings, and Th. Stöhlker
Radiative electron capture as a tunable source of highly linearly polarized x rays
Physical Review A 99, 052702 (2019)

Abstract: The radiative electron capture (REC) into the K shell of bare Xe ions colliding with a hydrogen gas target has been investigated. In this study, the degree of linear polarization of the K-REC radiation was measured and compared with rigorous relativistic calculations as well as with the previous results recorded for U92+. Owing to the improved detector technology, a significant gain in precision of the present polarization measurement is achieved compared to the previously published results. The obtained data confirms that for medium-Z ions such as Xe, the REC process is a source of highly polarized x rays which can easily be tuned with respect to the degree of linear polarization and the photon energy. We argue, in particular, that for relatively low energies the photons emitted under large angles are almost fully linear polarized.

A. Gumberidze, D. B. Thorn, A. Surzhykov, C. J. Fontes, B. Najjari, A. Voitkiv, S. Fritzsche, D. Banaś, H. F. Beyer, W. Chen, R. E. Grisenti, S. Hagmann, R. Hess, P.-M. Hillenbrand, P. Indelicato, C. Kozhuharov, M. Lestinsky, R. Märtin, N. Petridis, R. V. Popov, R. Schuch, U. Spillmann, S. Tashenov, S. Trotsenko, A. Warczak, G. Weber, W. Wen, D. F. A. Winters, N. Winters, Z. Yin, and Th. Stöhlker
Electron- and proton-impact excitation of heliumlike uranium in relativistic collisions
Physical Review A 99, 032706 (2019)

Abstract: We have studied the K-shell excitation of He-like uranium (U90+) in relativistic collisions with hydrogen and argon atoms. Performing measurements with different targets, as well as with different collision energies, enabled us to explore the proton- (nucleus-) impact excitation as well as the electron-impact excitation process for the heaviest He-like ion. The large fine-structure splitting in uranium allowed us to partially resolve excitation into different L-shell levels. State-of-the-art relativistic calculations which include excitation mechanisms due to the interaction with both protons (nucleus) and electrons are in good agreement with the experimental findings. Moreover, our experimental data clearly demonstrate the importance of including the generalized Breit interaction in the treatment of the electron-impact excitation process.

J. Glorius, C. Langer, Z. Slavkovská, L. Bott, C. Brandau, B. Brückner, K. Blaum, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, G. Gyürky, M. Heil, R. Hess, R. Hensch, P. Hillmann, P.-M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch, A. Khodaparast, T. Kisselbach, N. Klapper, C. Kozhuharov, D. Kurtulgil, G. Lane, C. Lederer-Woods, M. Lestinsky, S. Litvinov, Yu. A. Litvinov, B. Löher, F. Nolden, N. Petridis, U. Popp, T. Rauscher, M. Reed, R. Reifarth, M. S. Sanjari, D. Savran, H. Simon, U. Spillmann, M. Steck, T. Stöhlker, J. Stumm, A. Surzhykov, T. Szücs, T. T. Nguyen, A. Taremi Zadeh, B. Thomas, S. Yu. Torilov, H. Törnqvist, M. Träger, C. Trageser, S. Trotsenko, L. Varga, M. Volknandt, H. Weick, M. Weigand, C. Wolf, P. J. Woods, and Y. M. Xing
Approaching the Gamow Window with Stored Ions: Direct Measurement of ¹²⁴Xe(p,γ) in the ESR Storage Ring
Physical Review Letters 122, 092701 (2019)

Abstract: We report the first measurement of low-energy proton-capture cross sections of 124Xe in a heavy-ion storage ring. 124Xe^54+ ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The 125Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.

2018

T. Gassner, M. Trassinelli, R. Heß, U. Spillmann, D. Banas, K.-H. Blumenhagen, F. Bosch, C. Brandau, W. Chen, C. Dimopoulou, E. Förster, R. Grisenti, A. Gumberidze, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, P. Jagodzinski, T. Kämpfer, Ch. Kozhuharov, M. Lestinsky, D. Liesen, Yu. A. Litvinov, R. Loetzsch, B. Manil, R. Märtin, F. Nolden, N. Petridis, M. S. Sanjari, K. Schulze, M. Schwemlein, A. Simionovici, M. Steck, Th. Stöhlker, C. I. Szabo, S. Trotsenko, I. Uschmann, G. Weber, O. Wehrhan, N. Winckler, D. Winters, N. Winters, E. Ziegler, and H. Beyer
Wavelength-dispersive spectroscopy in the hard x-ray regime of a heavy highly-charged ion: the 1s Lamb shift in hydrogen-like gold
New Journal of Physics 20, 073033 (2018)

Abstract: Accurate spectroscopy of highly-charged high-Z ions in a storage ring is demonstrated to be feasible by the use of specially adapted crystal optics. The method has been applied for the measurement of the is Lamb shift in hydrogen-like gold (Au78+) in a storage ring through spectroscopy of the Lyman x-rays. This measurement represents the first result obtained for a high-Z element using high-resolution wavelength-dispersive spectroscopy in the hard x-ray regime, paving the way for sensitivity to higher-order QED effects.

2017

Y. Kozhedub, A. Bondarev, X. Cai, A. Gumberidze, S. Hagmann, C. Kozhuharov, I. Maltsev, G. Plunien, V. Shabaev, C. Shao, Th. Stöhlker, I. Tupitsyn, B. Yang, and D. Yu
Intensities of K-X-ray satellite and hypersatellite target radiation in Bi83+-Xe @70MeV/u collisions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 408, 31 (2017)

Abstract: Non-perturbative calculations of the relativistic quantum dynamics of electrons in the Bi83+-Xe collisions at 70 AMeV are performed. A method of calculation employs an independent particle model with effective single-electron Dirac-Kohn-Sham operator. Solving of the single-electron equations is based on the coupled-channel approach with atomic-like Dirac-Sturm-Fock orbitals, localized at the ions (atoms). Special attention is paid to the inner-shell processes. Intensities of the K satellite and hypersatellite target radiation are evaluated. The role of the relativistic effects is studied.

A. Gumberidze, C. Kozhuharov, R. Zhang, S. Trotsenko, Y. Kozhedub, R. DuBois, H. Beyer, K.-H. Blumenhagen, C. Brandau, A. Bräuning-Demian, W. Chen, O. Forstner, B. Gao, T. Gassner, R. Grisenti, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, A. Kumar, M. Lestinsky, Yu. A. Litvinov, N. Petridis, D. Schury, U. Spillmann, C. Trageser, M. Trassinelli, X. Tu, and Th. Stöhlker
Impact parameter sensitive study of inner-shell atomic processes in the experimental storage ring
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 408, 27 (2017)

Abstract: In this work, we present a pilot experiment in the experimental storage ring (ESR) at GSI devoted to impact parameter sensitive studies of inner shell atomic processes for low-energy (heavy-) ion-atom collisions. The experiment was performed with bare and He-like xenon ions (Xe54+, Xe52+) colliding with neutral xenon gas atoms, resulting in a symmetric collision system. This choice of the projectile charge states was made in order to compare the effect of a filled K-shell with the empty one. The projectile and target X-rays have been measured at different observation angles for all impact parameters as well as for the impact parameter range of ∼35–70 fm.

M. Herdrich, G. Weber, A. Gumberidze, Z. Wu, and Th. Stöhlker
Fast calculator for X-ray emission due to Radiative Recombination and Radiative Electron Capture in relativistic heavy-ion atom collisions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 408, 294 (2017)

Abstract: Abstract In experiments with highly charged, fast heavy ions the Radiative Recombination (RR) and Radiative Electron Capture (REC) processes have significant cross sections in an energy range of up to a few GeV / u . They are some of the most important charge changing processes in collisions of heavy ions with atoms and electrons, leading to the emission of a photon along with the formation of the ground and excited atomic states. Hence, for the understanding and planning of experiments, in particular for X-ray spectroscopy studies, at accelerator ring facilities, such as FAIR, it is crucial to have a good knowledge of these cross sections and the associated radiation characteristics. In the frame of this work a fast calculator, named RECAL, for the RR and REC process is presented and its capabilities are demonstrated with the analysis of a recently conducted experiment at the Experimental Storage Ring (ESR) at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. A method is presented to determine unknown X-ray emission cross sections via normalization of the recorded spectra to REC cross sections calculated by RECAL.

2016

K.-H. Blumenhagen, S. Fritzsche, T. Gassner, A. Gumberidze, R. Märtin, N. Schell, D. Seipt, U. Spillmann, A. Surzhykov, S. Trotsenko, G. Weber, V. A. Yerokhin, and Th. Stöhlker
Polarization transfer in Rayleigh scattering of hard x-rays
New Journal of Physics 18, 103034 (2016)

Abstract: We report on the first elastic hard x-ray scattering experiment where the linear polarization characteristics of both the incident and the scattered radiation were observed. Rayleigh scattering was investigated in a relativistic regime by using a high- Z target material, namely gold, and a photon energy of 175 keV. Although the incident synchrotron radiation was nearly 100% linearly polarized, at a scattering angle of θ=90° we observed a strong depolarization for the scattered photons with a degree of linear polarization of +27% ± 12% only. This finding agrees with second-order quantum electrodynamics calculations of Rayleigh scattering, when taking into account a small polarization impurity of the incident photon beam which was determined to be close to 98%. The latter value was obtained independently from the elastic scattering by analyzing photons that were Compton-scattered in the target. Moreover, our results indicate that when relying on state-of-the-art theory, Rayleigh scattering could provide a very accurate method to diagnose polarization impurities in a broad region of hard x-ray energies.

M. Lestinsky, V. Andrianov, B. Aurand, V. Bagnoud, D. Bernhardt, H. Beyer, S. Bishop, K. Blaum, A. Bleile, At. Borovik, F. Bosch, C. Bostock, C. Brandau, A. Bräuning-Demian, I. Bray, T. Davinson, B. Ebinger, A. Echler, P. Egelhof, A. Ehresmann, M. Engström, C. Enss, N. Ferreira, D. Fischer, A. Fleischmann, E. Förster, S. Fritzsche, R. Geithner, S. Geyer, J. Glorius, K. Göbel, O. Gorda, J. Goullon, P. Grabitz, R. Grisenti, A. Gumberidze, S. Hagmann, M. Heil, A. Heinz, F. Herfurth, R. Heß, P.-M. Hillenbrand, R. Hubele, P. Indelicato, A. Källberg, O. Kester, O. Kiselev, A. Knie, C. Kozhuharov, S. Kraft-Bermuth, T. Kühl, G. Lane, Y. Litvinov, D. Liesen, X. Ma, R. Märtin, R. Moshammer, A. Müller, S. Namba, P. Neumayer, T. Nilsson, W. Nörtershäuser, G. G. Paulus, N. Petridis, M. Reed, R. Reifarth, P. Reiß, J. Rothhardt, R. Sanchez, M. Sanjari, S. Schippers, H. Schmidt, D. Schneider, P. Scholz, R. Schuch, M. Schulz, V. Shabaev, A. Simonsson, J. Sjöholm, Ö. Skeppstedt, K. Sonnabend, U. Spillmann, K. Stiebing, M. Steck, T. Stöhlker, A. Surzhykov, S. Torilov, E. Träbert, M. Trassinelli, S. Trotsenko, X. Tu, I. Uschmann, P. Walker, G. Weber, D. Winters, P. Woods, H. Zhao, and Y. Zhang
Physics book: CRYRING@ESR
European Physical Journal Special Topics 225, 797 (2016)

Abstract: The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm and at the Test Storage Ring (TSR) at Heidelberg. For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei.

P.-M. Hillenbrand, S. Hagmann, J. M. Monti, R. D. Rivarola, K.-H. Blumenhagen, C. Brandau, W. Chen, R. D. DuBois, A. Gumberidze, D. L. Guo, M. Lestinsky, Yu. A. Litvinov, A. Müller, S. Schippers, U. Spillmann, S. Trotsenko, G. Weber, and Th. Stöhlker
Strong asymmetry of the electron-loss-to-continuum cusp of multielectron U²⁸⁺ projectiles in near-relativistic collisions with gaseous targets
Physical Review A 93, 042709 (2016)

Abstract: The process of electron-loss to the continuum (ELC) has been studied for the collision systems U28+ -> H2 at a collision energy of 50 MeV/u, U28+ -> N2 at 30 MeV/u, and U28+ -> Xe at 50 MeV/u. The energy distributions of cusp electrons emitted at an angle of 0∘ with respect to the projectile beam were measured using a magnetic forward-angle electron spectrometer. For these collision systems far from equilibrium charge state, a significantly asymmetric cusp shape is observed. The experimental results are compared to calculations based on first-order perturbation theory, which predict an almost symmetric cusp shape. Some possible reasons for this discrepancy are discussed.

2015

A. Gumberidze, T. Stöhlker, and Y. Litvinov
Atomic physics at the future facility for antiproton and ion research: status report 2014
Physica Scripta 2015, 014076 (2015)

Abstract: In this contribution, a brief overview of the Stored Particle Atomic physics Research Collaboration scientific program at the upcoming Facility for Antiproton and Ion Research (FAIR) is given. The program comprises a very broad range of research topics addressing atomic structure and dynamics in hitherto unexplored regimes, light–matter interactions, lepton pair production phenomena, precision tests of quantum electrodynamics and standard model in the regime of extreme fields and many more. We also present the current strategy for the realization of the envisioned physics program within the modularized start version (MSV) of FAIR.

S. Tashenov, D. Banas, H. Beyer, C. Brandau, S. Fritzsche, A. Gumberidze, S. Hagmann, P.-M. Hillenbrand, H. Jörg, I. Kojouharov, C. Kozhuharov, M. Lestinsky, Y. A. Litvinov, A. V. Maiorova, H. Schaffner, V. M. Shabaev, U. Spillmann, T. Stöhlker, A. Surzhykov, and S. Trotsenko
Coherent population of magnetic sublevels of 2p₃/₂ state in hydrogenlike uranium by radiative recombination
Physica Scripta 2015, 014027 (2015)

Abstract: The x-rays emitted in the process of radiative recombination (RR) of quasi-free electrons into 2p₃/₂ excited state of hydrogenlike uranium ion were studied experimentally. Both the RR x-ray and the subsequently emitted Lyα₁ x-ray were detected in time-coincidences. The angular distribution of the Lyα₁ x-rays varied as a function of the RR x-ray emission direction. This observation revealed the coherent population of magnetic sublevels of the 2p₃/₂ state in the hydrogenlike uranium ion.

S. Trotsenko, A. Gumberidze, Y. Gao, C. Kozhuharov, S. Fritzsche, H. F. Beyer, S. Hagmann, P.-M. Hillenbrand, N. Petridis, U. Spillmann, A. Surzhykov, D. B. Thorn, G. Weber, and T. Stöhlker
Experimental study of the dielectronic recombination into Li-like uranium
Physica Scripta 2015, 014024 (2015)

Abstract: We have measured the x-rays following 116.15 MeV/u U⁸⁹⁺ collisions with H 2 at 35°, 90°, 120° and 150° observation angles with regard to the ion beam direction. From our experimental spectra combined with radiative electron capture calculations, we obtain angular distribution of characteristic x-rays L to K following the resonance transfer and excitation. Our result shows a good qualitative agreement with theoretical predictions.

K.-H. Blumenhagen, U. Spillmann, T. Gaßner, A. Gumberidze, R. Märtin, N. Schell, S. Trotsenko, G. Weber, and T. Stöhlker
Identification and reduction of unwanted stray radiation using an energy- and position-sensitive Compton polarimeter
Physica Scripta 2015, 014032 (2015)

Abstract: In this work, we report on an experiment that investigated the elastic scattering of linearly polarized 175 keV photons on a gold target. A combined measurement of the angular distribution and the linear polarization of the scattered photons was performed using standard germanium detectors and a double-sided Si(Li) strip polarimeter. Since the data analysis is still in progress, we will show results in forthcoming papers and present here how the polarimeter was used to identify a lack of shielding during the experiment.

D. T. Doherty, P. J. Woods, Y. A. Litvinov, M. Ali Najafi, S. Bagchi, S. Bishop, M. Bo, C. Brandau, T. Davinson, I. Dillmann, A. Estrade, P. Egelhof, A. Evdokimov, A. Gumberidze, M. Heil, C. Lederer, S. A. Litvinov, G. Lotay, N. Kalantar-Nayestanaki, O. Kiselev, C. Kozhuharov, T. Kröll, M. Mahjour-Shafei, M. Mutterer, F. Nolden, N. Petridis, U. Popp, R. Reifarth, C. Rigollet, S. Roy, M. Steck, T. Stöhlker, B. Streicher, S. Trotsenko, M. von Schmid, X. L. Yan, and J. C. Zamora
Nuclear transfer reaction measurements at the ESR—for the investigation of the astrophysical ¹⁵O(α,γ)¹⁹Ne reaction
Physica Scripta 2015, 014007 (2015)

Abstract: Astrophysical x-ray bursts are thought to be a result of thermonuclear explosions on the atmosphere of an accreting neutron star. Between these bursts, energy is thought to be generated by the hot CNO cycles. The ¹⁵O(α,γ)¹⁹Ne reaction is one reaction that allows breakout from these CNO cycles and into the rp-process to fuel outbursts. The reaction is expected to be dominated by a single 3/2⁺ resonance at 4.033 MeV in ¹⁹Ne, however, limited information is available on this key state. This work reports on a pioneering study of the ²⁰Ne(p,d)¹⁹Ne reaction, performed in inverse kinematics at the experimental storage ring (ESR) as a means of accessing the astrophysically important 4.033 MeV state in ¹⁹Ne. The unique, background free, high luminosity conditions of the storage ring were utilized for this, the first transfer reaction performed at the ESR. The results of this pioneering test experiment are presented along with suggestions for future measurements at storage ring facilities.

D. Banaś, M. Pajek, A. Surzhykov, Th. Stöhlker, C. Brandau, A. Gumberidze, C. Kozhuharov, H. F. Beyer, S. Böhm, F. Bosch, M. Czarnota, S. Chatterjee, J.-C. Dousse, S. Fritzsche, S. Hagmann, D. Liesen, P. H. Mokler, A. Müller, A. Kumar, R. Reuschl, D. Sierpowski, U. Spillmann, J. Szlachetko, S. Tashenov, S. Trotsenko, P. Verma, and A. Warczak
Subshell-selective x-ray studies of radiative recombination of U⁹²⁺ ions with electrons for very low relative energies
Physical Review A 92, 032710 (2015)

Abstract: Radiative recombination (RR) into the K shell and L subshells of U92+ ions interacting with cooling electrons has been studied in an x-ray RR experiment at the electron cooler of the Experimental Storage Ring at GSI. The measured radiative recombination rate coefficients for electron-ion relative energies in the range 0–1000 meV demonstrate the importance of relativistic effects. The observed asymmetry of the measured K-RR x-ray emission with respect to the cooling energy, i.e., zero average relative velocity (〈vrel〉=0), are explained by fully relativistic RR calculations. With our new approach, we show that the study of the angular distribution of RR photons for different relative energies opens new perspectives for detailed understanding of the RR of ions with cooling electrons in cold magnetized plasma.

A. Gumberidze, D. B. Thorn, C. J. Fontes, B. Najjari, H. L. Zhang, A. Surzhykov, A. Voitkiv, S. Fritzsche, D. Banaś, H. Beyer, W. Chen, R. D. DuBois, S. Geyer, R. E. Grisenti, S. Hagmann, M. Hegewald, S. Hess, C. Kozhuharov, R. Märtin, N. Petridis, R. Reuschl, A. Simon, U. Spillmann, M. Trassinelli, S. Trotsenko, G. Weber, D. F. A. Winters, N. Winters, D. Yu, and Th. Stöhlker
Ground-state excitation of heavy highly-charged ions
Journal of Physics B: Atomic, Molecular and Optical Physics 48, 144006 (2015)

Abstract: We have studied the excitation of H-like and He-like uranium (U^91+ and U^90+ ) in relativistic collisions with gaseous targets by observing the subsequent x-ray emission. The experiment was conducted at the ESR storage ring of the GSI accelerator facility in Darmstadt, Germany. The measurements were performed with a newly developed multi-phase target at different collision energies. This enabled us to explore the proton (nucleus) impact excitation as well as the electron impact excitation processes in the relativistic collisions. The large fine-structure splitting in uranium allowed us to unambiguously resolve excitation to different L-shell levels. Moreover, information about the population of different magnetic sublevels has been obtained via an angular differential study of the decay photons associated with the subsequent de-excitation process. The experimental results are compared with calculations performed within the relativistic framework including excitation mechanisms due to both protons (nucleus) and electrons.

H. F. Beyer, T. Gassner, M. Trassinelli, R. Heß, U. Spillmann, D. Banaś, K.-H. Blumenhagen, F. Bosch, C. Brandau, W. Chen, C. Dimopoulou, E. Förster, R. E. Grisenti, A. Gumberidze, S. Hagmann, P.-M. Hillenbrand, P. Indelicato, P. Jagodzinski, T. Kämpfer, C. Kozhuharov, M. Lestinsky, D. Liesen, Y. A. Litvinov, R. Loetzsch, B. Manil, R. Märtin, F. Nolden, N. Petridis, M. S. Sanjari, K. S. Schulze, M. Schwemlein, A. Simionovici, M. Steck, Th. Stöhlker, C. I. Szabo, S. Trotsenko, I. Uschmann, G. Weber, O. Wehrhan, N. Winckler, D. F. A. Winters, N. Winters, and E. Ziegler
Crystal optics for precision x-ray spectroscopy on highly charged ions—conception and proof
Journal of Physics B: Atomic, Molecular and Optical Physics 48, 144010 (2015)

Abstract: The experimental investigation of quantum-electrodydamic contributions to the binding energies of inner shells of highly charged heavy ions requires an accurate spectroscopy in the region of hard x-rays suitable at a limited source strength. For this purpose the focusing compensated asymmetric Laue crystal optics has been developed and a twin-spectrometer assembly has been built and commissioned at the experimental storage ring of the GSI Helmholtzzentrum Darmstadt. We characterize the crystal optics and demonstrate the usefulness of the instrumentation for accurate spectroscopy of both stationary and fast moving x-ray sources. The experimental procedures discussed here may also be applied for other spectroscopic studies where a transition from conventional germanium x-ray detectors to crystal spectrometers seems too demanding because of low source intensity.

P.-M. Hillenbrand, S. Hagmann, D. H. Jakubassa-Amundsen, J. M. Monti, D. Banaś, K.-H. Blumenhagen, C. Brandau, W. Chen, P. D. Fainstein, E. De Filippo, A. Gumberidze, D. L. Guo, M. Lestinsky, Yu. A. Litvinov, A. Müller, R. D. Rivarola, H. Rothard, S. Schippers, M. S. Schöffler, U. Spillmann, S. Trotsenko, X. L. Zhu, and Th. Stöhlker
Electron-capture-to-continuum cusp in U⁸⁸⁺+N₂ collisions
Physical Review A 91, 022705 (2015)

Abstract: For the collision system U88+ -> N2 at a collision energy of 90 MeV/u, the energy distribution of electrons being nonradiatively captured from the target into the projectile continuum has been measured under an angle of 0∘ with respect to the projectile beam axis. This measurement of the electron-capture-to-continuum cusp with the highest effective projectile charge Z_eff,p=88 at a near-relativistic collision velocity of β≈0.41 is shown to be characterized by a strong asymmetry in the cusp shape. By comparing the data to measurements of the radiative-electron-capture-to-continuum cusp for the same collision system, the opposite asymmetry of the cusp is traced back to the varying underlying mechanisms. The experimental results are compared with the two theoretical calculations available for this process, one of them in the semirelativistic impulse approximation and the other in the nonrelativistic continuum-distorted-wave approach. A corresponding fully relativistic treatment may be motivated by the presented experimental data.