We report on the first observation of the unbound proton-rich nucleus Ne-15. Its ground state and first excited state were populated in two-neutron knockout reactions from a beam of 500 MeV/u Ne-17. ...The Ne-15 ground state is found to be unbound by 2.522(66) MeV. The decay proceeds directly to O-13 with simultaneous two-proton emission. No evidence for sequential decay via the energetically allowed 2(-) and 1(-) states in F-14 is observed. The Ne-15 ground state is shown to have a strong configuration with two protons in the (sd) shell around O-13 with a 63(5)% (1s(1/2))(2) component.
The excited structure of the single-hole nucleus Sn 131 populated by the β − decay of In 131 was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric ...purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited ν h 11 / 2 neutron-hole state was confirmed via an independent mass spectroscopy experiment performed at the Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. The level scheme of Sn 131 was notably expanded with the addition of 31 new γ -ray transitions and 22 new excited levels. The γ -emitting excited levels above the neutron separation energy in Sn 131 were investigated, revealing a large number of states, which in some cases decay by transitions to other neutron-unbound states. Our analysis showed the dependence between the population of these states in Sn 131 and the β -decaying In 131 state feeding them. Profiting from the isomer selectivity, it was possible to estimate the direct β feeding to the 3 / 2 + ground and 11 / 2 − isomeric states, disentangling the contributions from the three indium parent states. This made possible to resolve the discrepancies in log f t for first-forbidden transitions observed in previous studies, and to determine the β -delayed neutron decay probability ( P n ) values of each indium isomers independently. The first measurement of subnanosecond lifetimes in Sn 131 was performed in this work. A short T 1 / 2 = 18 ( 4 ) − ps value was measured for the 1 / 2 + neutron single-hole 332-keV state, which indicates an enhanced l -forbidden M 1 behavior for the ν 3 s 1 / 2 − 1 → ν 3 d 3 / 2 − 1 transition. The measured half-lives of high-energy states populated in the β decay of the ( 21 / 2 + ) second isomeric state ( In 131 m 2 ) provided valuable information on transition rates, supporting the interpretation of these levels as core-excited states analogous to those observed in the doubly-magic Sn 132 . Published by the American Physical Society 2024
The study of nuclear decay modes reveals a large panel of nuclear structure phenomena and allows us to investigate the behaviour of the atomic nucleus with an extreme imbalance of the number of ...neutrons and protons with respect to stable nuclei. In the present paper, we review certain aspects of
β
-delayed decay modes, of one- and two-proton radioactivity, and of the experimental techniques which allowed us to get deep insights into the organisation of the atomic nucleus. In most cases, the study of these decay modes is the only means to obtain the information searched for. The investigation of nuclear decay modes is shown to be a powerful tool to study the most proton-rich nuclei and their nuclear structure.
Detailed study of the decay of 21Mg Jensen, E. A. M.; Nielsen, S. T.; Andreyev, A. ...
The European physical journal. A, Hadrons and nuclei,
2024, Letnik:
60, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Beta-delayed proton and gamma emission in the decay of
21
Mg has been measured at ISOLDE, CERN with the ISOLDE Decay Station (IDS) set-up. The existing decay scheme is updated, in particular what ...concerns proton transitions to excited states in
20
Ne. Signatures of interference in several parts of the spectrum are used to settle spin and parity assignments to highly excited states in
21
Na. The previously reported
β
p
α
branch is confirmed. A half-life of 120.5(4) ms is extracted for
21
Mg. The revised decay scheme is employed to test mirror symmetry in the decay and to extract the beta strength distribution of
21
Mg that is compared with theory.
The emission of neutron pairs from the neutron-rich N=12 isotones C18 and O20 has been studied by high-energy nucleon knockout from N19 and O21 secondary beams, populating unbound states of the two ...isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay N19(-1p)C18*→C16+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a C14 core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay O21(-1n)O20*→O18+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the O16 core and reduces the number of pairs.
The proton drip-line nucleus 17Ne is considered a good candidate for a Borromean two-proton halo with a 15O + p + p structure. Angular distributions of the elastic scattering and inclusive 15O ...production for a 136 MeV 17Ne beam incident on a 208Pb target were measured for the first time at the SPIRAL1 facility, GANIL. Use of the GLORIA detector array allowed high-resolution data over a wide angular range from 20∘ up to 95∘ in the laboratory frame to be obtained. The elastic scattering angular distribution shows similarities with those for both 6He and 20Ne at equivalent collision energies with respect to the corresponding Coulomb barriers, exhibiting the suppression of the Coulomb rainbow peak characteristic of strong coupling. Optical model and coupled channel fits suggest that this is due to a combination of coupling to low-lying quadrupole resonances and Coulomb dipole coupling to the low-lying continuum, although their relative importance depends on the relevant B(E2) values which remain to be firmly determined.
208Po populated through EC/β+ decay Brunet, M.; Berry, T.A.; Podolyák, Zs ...
Journal of physics. Conference series,
12/2020, Letnik:
1643, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The structure of 208Po resulting from the EC/β+ decay of 208At was studied at CERN's ISOLDE Decay Station (IDS). The high statistics afforded by the high yield of 208At and the high efficiency HPGe ...clusters at the IDS allowed for greater insight into lower intensity transitions and thus significant expansion of the 208Po level scheme. Furthermore, investigation into the isomeric state yielded a new half life 377(9) ns in addition to uncovering new transitions populating the state.
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