| 1. |
- Illana, A., et al.
(författare)
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Coulomb excitation of 74,76Zn
- 2023
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Ingår i: Physical Review C. - 2469-9985. ; 108:4
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Tidskriftsartikel (refereegranskat)abstract
- The first experiment using radioactive beams post-accelerated by the HIE-ISOLDE facility has enabled to obtain a precise set of B(E2) transition probabilities in neutron-rich 74,76Zn isotopes. The resulting B(E2; 2+1→0+1) values are consistent with those determined in earlier REX-ISOLDE measurements. While the B(E2; 4+1→2+1) transition probability in 76Zn is also in agreement with earlier Coulomb-excitation results, the value obtained for 74Zn is considerably lower. For the first time, a spectroscopic quadrupole moment of the 2+1 state was measured for an exotic nucleus in this mass region. A detailed comparison is presented with large-scale shell-model and Monte Carlo shell-model calculations.
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| 2. |
- Urquiza-González, M., et al.
(författare)
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Benchmark evaluation for a single frequency continuous wave OPO seeded pulsed dye amplifier for high-resolution laser spectroscopy
- 2023
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781510659032
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Konferensbidrag (refereegranskat)abstract
- The study of the atomic spectrum via resonant laser excitation provides access to underlying effects caused by the nuclear structure, which is of special interest in short-lived radioisotopes produced at Isotope Separator On-Line (ISOL) facilities. Current implementations of resonant laser ionization techniques often limit the extraction of the nuclear observables due to the low spectral resolution of the pulsed laser systems deployed. Several high-resolution spectroscopy techniques demand spectral widths in the order of hundreds of MHz and below. A proven solution to reduce this linewidth is the pulsed amplification of a narrow-band continuous wave (cw) laser. This work presents the demonstration of a pulsed dye amplifier seeded by a commercially available cw Optical Parametric Oscillator (OPO). The performance of this system was compared with competing setups using a cw dye laser seed source as well as a frequency mixing technique using a combination of an injection-locked titanium:sapphire (Ti:Sa) and a Nd:YVO4 laser. Spectral bandwidths of the systems were measured using a high finesse Fabry-Perot Interferometer, resulting in comparable optical linewidths between 140 to 156 MHz at a wavelength of 328 nm for the different laser setups. Suitability for on-line experiments was validated by performing high-resolution spectroscopy of radioactive silver isotopes in the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the Isotope Separator On-Line Device (ISOLDE), at the European Organization for Nuclear Research (CERN). The quality of the hyperfine spectra was similar for the dye and the OPO seed and the deduced hyperfine splitting was in good agreement with literature, while the frequency mixing technique exhibited less precise results attributed to the frequency instabilities and mode-hops of the single-mode Nd:YVO4 laser.
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| 3. |
- Barzakh, A., et al.
(författare)
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Large Shape Staggering in Neutron-Deficient Bi Isotopes
- 2021
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Ingår i: Physical Review Letters. - 0031-9007. ; 127:19
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Tidskriftsartikel (refereegranskat)abstract
- The changes in the mean-square charge radius (relative to Bi209), magnetic dipole, and electric quadrupole moments of Bi187,188,189,191 were measured using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). A large staggering in radii was found in Bi187,188,189g, manifested by a sharp radius increase for the ground state of Bi188 relative to the neighboring Bi187,189g. A large isomer shift was also observed for Bi188m. Both effects happen at the same neutron number, N=105, where the shape staggering and a similar isomer shift were observed in the mercury isotopes. Experimental results are reproduced by mean-field calculations where the ground or isomeric states were identified by the blocked quasiparticle configuration compatible with the observed spin, parity, and magnetic moment. © 2021 authors.
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| 4. |
- Rothe, Sebastian, et al.
(författare)
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Laser photodetachment of radioactive I-128(-)
- 2017
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Ingår i: Journal of Physics G-Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 44:10
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Tidskriftsartikel (refereegranskat)abstract
- The first experimental investigation of the electron affinity (EA) of a radioactive isotope has been conducted at the CERN-ISOLDE radioactive ion beam facility. The EA of the radioactive iodine isotope I-128 (t(1/2) = 25 min) was determined to be 3.059 052(38) eV. The experiment was conducted using the newly developed Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment (GANDALPH) apparatus, connected to a CERNI-SOLDE experimental beamline. I-128 was produced in fission induced by 1.4 GeV protons striking a thorium/tantalum foil target and then extracted as singly charged negative ions at a beam energy of 20 keV. Laser photodetachment of the fast ion beam was performed in a collinear geometry inside the GANDALPH chamber. Neutral atoms produced in the photodetachment process were detected by allowing them to impinge on a glass surface, creating secondary electrons which were then detected using a channel electron multiplier. The photon energy of the laser was tuned across the threshold of the photodetachment process and the detachment threshold data were fitted to a Wigner law function in order to extract the EA. This first successful demonstration of photodetachment at an isotope separator on line facility opens up the opportunity for future studies of the fundamental properties of negatively charged radioactive isotopes such as the EA of astatine and polonium.
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| 5. |
- Udrescu, S. M., et al.
(författare)
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Precision spectroscopy and laser-cooling scheme of a radium-containing molecule
- 2024
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Ingår i: NATURE PHYSICS. - 1745-2473 .- 1745-2481.
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Tidskriftsartikel (refereegranskat)abstract
- Molecules containing heavy radioactive nuclei are predicted to be extremely sensitive to violations of the fundamental symmetries of nature. The nuclear octupole deformation of certain radium isotopes massively boosts the sensitivity of radium monofluoride molecules to symmetry-violating nuclear properties. Moreover, these molecules are predicted to be laser coolable. Here we report measurements of the rovibronic structure of radium monofluoride molecules, which allow the determination of their laser cooling scheme. We demonstrate an improvement in resolution of more than two orders of magnitude compared to the state of the art. Our developments allowed measurements of minuscule amounts of hot molecules, with only a few hundred per second produced in a particular rotational state. The combined precision and sensitivity achieved in this work offer opportunities for studies of radioactive molecules of interest in fundamental physics, chemistry and astrophysics. Measurements of the rovibronic structure of radium monofluoride molecules allow the identification of a laser cooling scheme. This will enable precise tests of fundamental physics, such as searches for parity or time-reversal symmetry violation.
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| 6. |
- Andel, B., et al.
(författare)
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β -delayed fission of isomers in Bi 188
- 2020
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Ingår i: Physical Review C. - 2469-9985. ; 102:1
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Tidskriftsartikel (refereegranskat)abstract
- β-delayed fission (βDF) decay of a low-spin (ls) and a high-spin (hs) isomer in Bi188 was studied at the ISOLDE facility at CERN. Isomer-selective laser ionization and time gating were employed to investigate each isomer separately and their βDF partial half-lives were determined: T1/2p,βDF(188Bihs)=5.6(8)×103 s and T1/2p,βDF(188Bils)=1.7(6)×103 s. This work is the first βDF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide Pb188, following the β decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes. Experimental results were compared with self-consistent mean-field calculations based on the finite-range Gogny D1M interaction. To reproduce the measured T1/2p,βDF(188Bihs), the calculated fission barrier of Pb188 had to be reduced by ≈30%. After this reduction, the measured T1/2p,βDF(188Bils) was in agreement with calculations for a few possible configurations for Bils188. Theoretical βDF probabilities for these configurations were found to be lower by a factor of 4-9 than the βDF probability of Bihs188. The fission fragment mass distribution of Pb188 was compared to the scission-point model SPY and the calculations based on the finite-range liquid-drop model. The first observation of βDF for Bi190 is also reported. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
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| 7. |
- Au, M., et al.
(författare)
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In-source and in-trap formation of molecular ions in the actinide mass range at CERN-ISOLDE
- 2023
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Ingår i: Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms. - 0168-583X. ; 541, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- 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+, UO1-3+, UC1-3+, UF1-4+, UF1,2O1,2+ are reported. Metastable tantalum and uranium fluoride molecular ions are identified. Formation of UO1-3+, U(OH)1-3+, UC1-3+, UF1,2O1,2+ from mass-separated beams of U+, UF1,2+ with residual gas is observed in the ion trap. The effect of trapping time on molecular formation is presented.
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| 8. |
- Ballof, J., et al.
(författare)
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A concept for the extraction of the most refractory elements at CERN-ISOLDE as carbonyl complex ions
- 2022
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 58:5
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a novel thick-target concept tailored to the extraction of refractory 4d and 5d transition metal radionuclides of molybdenum, technetium, ruthenium and tungsten for radioactive ion beam production. Despite the more than 60-year old history of thick-target ISOL mass-separation facilities like ISOLDE, the extraction of these most refractory elements as radioactive ion beam has so far not been successful. In ordinary thick ISOL targets, their radioisotopes produced in the target are stopped within the condensed target material. Here, we present a concept which overcomes limitations associated with this method. We exploit the recoil momentum of nuclear reaction products for their release from the solid target material. They are thermalized in a carbon monoxide-containing atmosphere, in which volatile carbonyl complexes form readily at ambient temperature and pressure. This compound serves as volatile carrier for transport to the ion source. Excess carbon monoxide is removed by cryogenic gas separation to enable low pressures in the source region, in which the species are ionized and hence made available for radioactive ion beam formation. The setup is operated in batch mode. Initially, we investigate the feasibility of the approach with isotopes of more than 35s half-life. At the cost of reduced efficiency, the concept could also be applied to isotopes with half-lives of at least one to 10s. We report parameter studies of the key processes of the method, which validate this concept and which define the parameters for the setup. This would allow for the first time the extraction of radioactive molybdenum, tungsten and several other transition metals at thick-target ISOL facilities.
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| 9. |
- Leimbach, David, 1992, et al.
(författare)
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The electron affinity of astatine
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- One of the most important properties influencing the chemical behavior of an element is the electron affinity (EA). Among the remaining elements with unknown EA is astatine, where one of its isotopes, 211At, is remarkably well suited for targeted radionuclide therapy of cancer. With the At− anion being involved in many aspects of current astatine labeling protocols, the knowledge of the electron affinity of this element is of prime importance. Here we report the measured value of the EA of astatine to be 2.41578(7) eV. This result is compared to state-of-the-art relativistic quantum mechanical calculations that incorporate both the Breit and the quantum electrodynamics (QED) corrections and the electron–electron correlation effects on the highest level that can be currently achieved for many-electron systems. The developed technique of laser-photodetachment spectroscopy of radioisotopes opens the path for future EA measurements of other radioelements such as polonium, and eventually super-heavy elements.
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| 10. |
- Rothe, S., et al.
(författare)
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Targets and ion sources at CERN-ISOLDE - Facilities and developments
- 2023
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Ingår i: Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms. - 0168-583X. ; 542, s. 38-44
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Tidskriftsartikel (refereegranskat)abstract
- At the CERN-ISOLDE radioactive ion beam facility, thick targets are irradiated using a beam of 1.4-GeV protons. One of ISOLDE's key features is the large choice of ion source types and target materials available, enabling us to select the ideal combination for optimal intensity and purity of the isotopes requested by ISOLDE users. The ever-increasing demands in terms of isotope production yield, beam purity, and overall reliability of the employed systems are driving the continuous development efforts.Over the past few years, CERN has invested heavily in facilities and infrastructure that facilitate ongoing developments required for ISOLDE. A dedicated offline laboratory (Offline 2) has been recently equipped with high repetition rate nanosecond tunable lasers required for scheme development and developments of specialized laser ion source types such as VADLIS, LIST and PI-LIST. Moreover, it hosts a twin setup of the ISOLDE RFQ cooler and buncher (ISCOOL), which is envisaged to be used for studies of molecular beam creation and breakup, as well as the development of improved RFQ services and operational modes. For material development, particularly for nanostructured materials, the new nano laboratory has just been commissioned and will enable the production and development of nano actinide targets for ISOLDE. In this contribution we describe the infrastructure required for target and ion source developments, highlight recent efforts and experimental results on both target material development and ion source development, and provide an outlook on what to expect in the near future.
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