0000000000522229
AUTHOR
U. Köster
showing 15 related works from this author
On-line yields obtained with the ISOLDE RILIS
2003
The ISOLDE resonance ionization laser ion source (RILIS) allows to ionize efficiently and selectively many metallic elements. In recent yield surveys and on-line experiments with the ISOLDE RILIS we observed 23–34 Mg, 26–34 Al, 98–132 Cd, 149 Tb, 155–177 Yb, 179–200 Tl, 183–215 Pb and 188–218 Bi. The obtained yields are presented together with measured release parameters which allow to extrapolate the release efficiency towards more exotic (short-lived) nuclides of the same elements. 2002 Elsevier Science B.V. All rights reserved.
Atomic spectroscopy studies of short-lived isotopes and nuclear isomer separation with the ISOLDE RILIS
2002
The Resonance Ionization Laser Ion Source (RILIS) at the ISOLDE on-line isotope separator is based on the selective excitation of atomic transitions by tunable laser radiation. Ion beams of isotopes of 20 elements have been produced using the RILIS setup. Together with the mass separator and a particle detection system it represents a tool for high-sensitive laser spectroscopy of short-lived isotopes. By applying narrow-bandwidth lasers for the RILIS one can study isotope shifts (IS) and hyperfine structure (HFS) of atomic optical transitions. Such measurements are capable of providing data on nuclear charge radii, spins and magnetic moments of exotic nuclides far from stability. Although t…
Measurement of the first ionization potential of astatine by laser ionization spectroscopy
2013
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to sup…
The Miniball spectrometer
2013
The Miniball germanium detector array has been operational at the REX (Radioactive ion beam EXperiment) post accelerator at the Isotope Separator On-Line facility ISOLDE at CERN since 2001. During the last decade, a series of successful Coulomb excitation and transfer reaction studies have been performed with this array, utilizing the unique and high-quality radioactive ion beams which are available at ISOLDE. In this article, an overview is given of the technical details of the full Miniball setup, including a description of the γ-ray and particle detectors, beam monitoring devices and methods to deal with beam contamination. The specific timing properties of the REX-ISOLDE facility are hi…
New states in heavy Cd isotopes and evidence for weakening of the N = 82 shell structure
2000
A chemically selective laser ion source has been used in a β-decay study of heavy Ag isotopes into even-even Cd nuclides. Gamma-spectroscopic techniques in time-resolving event-by-event and multiscaling modes have permitted the identification of the first 2+ and 4+ levels in 126Cd78, 128Cd80, and tentatively the 2+ state in 130Cd82. From a comparison of these new states in 48Cd with the E(2+) and E(4+)/E(2+) level systematics of 46Pd and 52Te isotopes and several recent model predictions, possible evidence for a weakening of the spherical N = 82 neutron-shell below double-magic 132Sn is obtained.
Decay of Neutron-Rich Mn Nuclides and Deformation of Heavy Fe Isotopes
1998
The use of chemically selective laser ionization combined with beta-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms Mn-61 up through 14-ms Mn-69. The measured half-lives are found to be significantly longer near N=40 than the values calculated with a QRPA shell model using ground-state deformations from the FRDM and ETFSI models. Gamma-ray singles and coincidence spectroscopy has been performed for Mn-64 and Mn-66 decays to levels of Fe-64 and Fe-66, revealing a significant drop in the energy of the first 2+ state in these nuclides that suggests an unanticipated increase in collectivity near N=40.
Measurement of the Magnetic Moment of the One-Neutron Halo NucleusB11e
1999
The magnetic moment of ${}^{11}\mathrm{Be}$ ( ${T}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13.8\phantom{\rule{0ex}{0ex}}\mathrm{s}$) was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a ${}^{11}{\mathrm{Be}}^{+}$ ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal, and observation of rf resonances in the asymmetric angular distribution of the $\ensuremath{\beta}$ decay ( $\ensuremath{\beta}$-NMR). The nuclear magnetic moment $\ensuremath{\mu}{(}^{11}\mathrm{Be})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}1.6816(8…
Changes in mean-squared charge radii and magnetic moments of $^{179–184}$Tl measured by in-source laser spectroscopy
2017
Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron-deficient isotopes 179–184Tl using the 276.9-nm transition. The experiment has been performed at the CERN-Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in 179,181,183Tl have been determined as I=1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in 182,184Tl from the trend…
Production of neptunium and plutonium nuclides from uranium carbide using 1.4-GeV protons
2023
Accelerator-based techniques are one of the leading ways to produce radioactive nuclei. In this work, the Isotope Separation On-Line method was employed at the CERN-ISOLDE facility to produce neptunium and plutonium from a uranium carbide target material using 1.4-GeV protons. Neptunium and plutonium were laser-ionized and extracted as 30-keV ion beams. A Multi-Reflection Time-of-Flight mass spectrometer was used for ion identification by means of time-of-flight measurements as well as for isobaric separation. Isotope shifts were investigated for the 395.6-nm ground state transition in $^{236,237,239}$Np and the 413.4-nm ground state transition in $^{236,239,240}$Pu. Rates of $^{235-241}$Np…
Evolution of deformation in neutron-rich Ba isotopes up to A=150
2018
12 pags., 11 figs., 3 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0
Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances
2005
4 pages, 3 figures.-- PMID: 15650733 [PubMed].
Shape coexistence in the odd-odd nucleus 98Y : the role of the g9/2 neutron extruder
2017
Excited states in 98Y, populated in neutron-induced fission of 235U and in spontaneous fission of 248Cm and 252Cf, have been studied by means of γ spectroscopy using the Lohengrin fission-fragment separator at ILL Grenoble and the EXILL, Eurogam2, and Gammasphere Ge arrays. Two new isomers have been found in 98Y: a deformed one with T1/2 = 180(7) ns and a rotational band on top of it, and a spherical one with T1/2 = 0.45(15)μs, analogous to the 8+ isomer in 96Y, corresponding to the (νg7/2,πg9/2)8+ spherical configuration. Using the JYFLTRAP Penning trap, an accurate excitation energy of 465.7(7) keV has been determined for the 2.36-s isomer in 98Y. This result and the studies of excited le…
In-source and in-trap formation of molecular ions in the actinide mass range at CERN-ISOLDE
2023
The use of radioactive molecules for fundamental physics research is a developing interdisciplinary field limited dominantly by their scarce availability. In this work, radioactive molecular ion beams containing actinide nuclei extracted from uranium carbide targets are produced via the Isotope Separation On-Line technique at the CERN-ISOLDE facility. Two methods of molecular beam production are studied: extraction of molecular ion beams from the ion source, and formation of molecular ions from the mass-separated ion beam in a gas-filled radio-frequency quadrupole ion trap. Ion currents of U$^+$, UO$_{1-3}^+$, UC$_{1-3}^+$, UF$_{1-4}^+$, UF$_{1,2}$O$_{1,2}^+$ are reported. Metastable tantal…
Measurement of the 7Be(n,p) cross section at thermal energy
2019
The 7Be(n,p) cross section was measured with an ion-implanted 7Be target at a thermal neutron beam of the research reactor LVR-15 in Řež. The cross section to the ground state of 7Li is σ(n,p0)=43800±1400b and the cross section to the first excited state of 7Li is σ(n,p1)=520±260b.
High-sensitivity study of levels in 30Al following β decay of 30Mg
2016
γ -ray and fast-timing spectroscopy were used to study levels in 30Al populated following the β− decay of 30Mg. Five new transitions and three new levels were located in 30Al. A search was made to identify the third 1+ state expected at an excitation energy of ∼2.5 MeV. Two new levels were found, at 3163.9 and 3362.5 keV, that are firm candidates for this state. Using the advanced time-delayed (ATD) βγγ (t) method we have measured the lifetime of the 243.8-keV state to be T1/2 = 15(4) ps, which implies that the 243.8-keV transition is mainly of M1 character. Its fast B(M1; 2+ → 3+) value of 0.10(3) W.u. is in very good agreement with the USD shell-model prediction of 0.090 W.u. The 1801.5-k…