0000000000373237
AUTHOR
D. Pauwels
showing 10 related works from this author
New developments of the in-source spectroscopy method at RILIS/ISOLDE
2013
At the CERN ISOLDE facility, long isotope chains of many elements are produced by proton-induced reactions in target materials such as uranium carbide. The Resonance Ionization Laser Ion Source (RILIS) is an efficient and selective means of ionizing the reaction products to produce an ion beam of a chosen isotope. Coupling the RILIS with modern ion detection techniques enables highly sensitive studies of nuclear properties (spins, electromagnetic moments and charge radii) along an isotope chain, provided that the isotope shifts and hyperfine structure splitting of the atomic transitions can be resolved. At ISOLDE the campaign to measure the systematics of isotopes in the lead region (Pb, Bi…
β-delayed fission andαdecay ofAt196
2016
A nuclear-decay spectroscopy study of the neutron-deficient isotope $^{196}\mathrm{At}$ is reported where an isotopically pure beam was produced using the selective Resonance Ionization Laser Ion Source and On-Line Isotope Mass Separator (CERN). The fine-structure $\ensuremath{\alpha}$ decay of $^{196}\mathrm{At}$ allowed the low-energy excited states in the daughter nucleus $^{192}\mathrm{Bi}$ to be investigated. A $\ensuremath{\beta}$-delayed fission study of $^{196}\mathrm{At}$ was also performed. A mixture of symmetric and asymmetric fission-fragment mass distributions of the daughter isotope $^{196}\mathrm{Po}$ (populated by $\ensuremath{\beta}$ decay of $^{196}\mathrm{At}$) was deduce…
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…
Tz=−1→0βdecays ofNi54,Fe50,Cr46, andTi42and comparison with mirror(He3,t)measurements
2015
We have studied the β decay of the Tz=−1, f7/2 shell nuclei Ni54, Fe50, Cr46, and Ti42 produced in fragmentation reactions. The proton separation energies in the daughter Tz=0 nuclei are relatively large (≈4–5 MeV) so studies of the γ rays are essential. The experiments were performed at GSI as part of the Stopped-beam campaign with the RISING setup consisting of 15 Euroball Cluster Ge detectors. From the newly obtained high precision β-decay half-lives, excitation energies, and β branching ratios, we were able to extract Fermi and Gamow-Teller transition strengths in these β decays. With these improved results it was possible to compare in detail the Gamow-Teller (GT) transition strengths …
Pairing-excitation versus intruder states inNi68andZr90
2010
A discussion on the nature of the 0{sup +} states in {sup 68}Ni (Z=28, N=40) is presented and a comparison is made with its valence counterpart {sup 90}Zr (Z=40, N=50). Evidence is given for a 0{sup +} proton-intruder state at only {approx}2.2-MeV excitation energy in {sup 68}Ni, while the analogous neutron-intruder states in {sup 90}Zr reside at 4126 and 5441 keV. The application of a shell-model description of 0{sup +} intruder states reveals that many pair-scattered neutrons across N=40 have to be involved to explain the low excitation energy of the proton-intruder configuration in {sup 68}Ni.
Performance of a high repetition pulse rate laser system for in-gas-jet laser ionization studies with the Leuven laser ion source @ LISOL
2012
The Leuven Isotope Separator On-Line (LISOL) facility at the Cyclotron Research Center (CRC) Louvain-la-Neuve; The laser ionization efficiency of the Leuven gas cell-based laser ion source was investigated under on- and off-line conditions using two distinctly different laser setups: a low-repetition rate dye laser system and a high-repetition rate Ti:sapphire laser system. A systematic study of the ion signal dependence on repetition rate and laser pulse energy was performed in off-line tests using stable cobalt and copper isotopes. These studies also included in-gas-jet laser spectroscopy measurements on the hyperfine structure of 63Cu. A final run under on-line conditions in which the ra…
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…
Gamow–Teller transitions in exotic pf-shell nuclei relevant to supernova explosion
2007
Gamow–Teller (GT) transitions starting from unstable pf-shell nuclei are of interest not only in nuclear physics, but also in astrophysics, e.g. in violent neutrino induced reactions at the core-collapse stage of type II supernovae. In the β-decay study of these pf-shell nuclei, half-lives can be measured rather accurately. On the other hand, in high-resolution (3He, t) charge-exchange reactions at 0°, individual GT transitions up to high excitations can be studied. Assuming the isospin symmetry for the strengths of Tz = ±1 → 0 analogous GT transitions, we present a unique 'merged analysis' for the determination of absolute B(GT) values.
Charge radii and electromagnetic moments of At195–211
2018
Hyperfine-structure parameters and isotope shifts of At195-211 have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass Spectrometer, in connection with a high-resolution electron multiplier, was used as an ion-counting setup for isotopes that either were affected by strong isobaric contamination or possessed a long half-life; the ISOLDE Faraday cups were used for cases with high-intensity beams; and the Windmill decay station was used for short-lived, predominantl…
First application of the Laser Ion Source and Trap (LIST) for on-line experiments at ISOLDE
2012
The Laser Ion Source and Trap (LIST) provides a new mode of operation for the resonance ionization laser ion source (RILIS) at ISOLDE/CERN, reducing the amount of surface-ionized isobaric contaminants by up to four orders of magnitude. After the first successful on-line test at ISOLDE in 2011 the LIST was further improved in terms of efficiency, selectivity, and reliability through several off-line tests at Mainz University and at ISOLDE. In September 2012, the first on-line physics experiments to use the LIST took place at ISOLDE. The measurements of the improved LIST indicate more than a twofold increase in efficiency compared to the LIST of the 2011 run. The suppression of surface-ionize…