A measurement of the final state distribution of the (8)B β decay, obtained by implanting a (8)B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent ...with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jyväskylä O. S. Kirsebom et al., Phys. Rev. C 83, 065802 (2011). It shows discrepancies with previously measured spectra, leading to differences in the derived neutrino spectrum. Thanks to a low detection threshold, the neutrino spectrum is for the first time directly extracted from the measured final state distribution, thus avoiding the uncertainties related to the extrapolation of R-matrix fits. Combined with the IGISOL data, this leads to an improvement of the overall errors and the extension of the neutrino spectrum at high energy. The new unperturbed neutrino spectrum represents a benchmark for future measurements of the solar neutrino flux as a function of energy.
Single-neutron states in the Z=30, N=49 isotope 79Zn have been populated using the 78Zn(d, p)79Zn transfer reaction at REX-ISOLDE, CERN. The experimental setup allowed the combined detection of ...protons ejected in the reaction, and of γ rays emitted by 79Zn. The analysis reveals that the lowest excited states populated in the reaction lie at approximately 1 MeV of excitation, and involve neutron orbits above the N=50 shell gap. From the analysis of γ-ray data and of proton angular distributions, characteristic of the amount of angular momentum transferred, a 5/2+ configuration was assigned to a state at 983 keV. Comparison with large-scale-shell-model calculations supports a robust neutron N=50 shell-closure for 78Ni. These data constitute an important step towards the understanding of the magicity of 78Ni and of the structure of nuclei in the region.
KISS (KEK Isotope Separation System) has been constructed at Nishina Research Center (NRC) of RIKEN to study the decay properties of heavy neutron-rich isotopes with mass number around A~200 along ...the neutron magic number of N = 126 for the astrophysical interest. The isotopes of interest will be produced by multi-nucleon transfer reactions in neutron-rich heavy ion collisions (e.g. super(136)Xe projectile on super(198)Pt target). KISS consists of a gas-cell system for thermalizing (stopping and neutralizing) and fast-transporting reaction products to the gas cell exit hole, a laser system for the resonant ionization, and a mass-separator system followed by a detection system for the decay spectroscopy. KISS will allow us to study unknown isotopes produced in weak reaction channels under low background conditions. The off-line test of the KISS has been finished. As a next step, on-line test experiments have been performed to investigate the overall efficiency and selectivity of the system as a function of the injected super(56)Fe beam intensity from the RIKEN Ring Cyclotron (RRC).
Collective 2+1 excitations in 206Po and 208,210Rn Grahn, T.; Pakarinen, J.; Jokiniemi, L. ...
The European physical journal. A, Hadrons and nuclei,
2016/11, Letnik:
52, Številka:
11
Journal Article
Recenzirano
.
In the present study,
B
(
E
2
;
2
1
+
→
0
1
+
)
values have been measured in the
208,210
Rn and
206
Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at ...CERN-ISOLDE. These nuclei have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist. However, contributions from collective excitations are likely to be present when moving away from the
N
=126 closed shell. Such an effect is confirmed by the observed increased collectivity of the
2
1
+
→
0
1
+
transitions. Experimental results have been interpreted with the aid of theoretical studies carried out within the BCS-based QRPA framework.
The νg9/2,d5/2,s1/2 orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below 68Ni. Especially the single-particle energies and strengths of these ...orbitals are of importance. We studied such properties in the nearby 67Ni nucleus, by performing a (d,p)-experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball γ-detection array and a newly-developed delayed-correlation technique as to investigate μs-isomers. Angular distributions of the ground state and multiple excited states in 67Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial νg9/2 (1007 keV) and νd5/2 (2207 keV and 3277 keV) single-particle strengths up to an excitation energy of 5.8 MeV. 50% of the νd5/2 single-particle strength relative to the νg9/2-orbital is concentrated in and shared between the first two observed 5/2+ levels. A comparison with extended Shell Model calculations and equivalent (3He, d) studies in the region around 9040Zr50 highlights similarities for the strength of the negative-parity pf and positive-parity g9/2 state, but differences are observed for the d5/2 single-particle strength.
Beta-delayed proton emission from 20Mg Lund, M. V.; Andreyev, A.; Borge, M. J. G. ...
The European physical journal. A, Hadrons and nuclei,
2016, Letnik:
52, Številka:
10
Journal Article
Recenzirano
Odprti dostop
.
Beta-delayed proton emission from
20
Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of ...27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in
20
Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in
20
Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in
19
Ne through the beta decay of
20
Mg, which is important for the astrophysically relevant reaction
15
O(
,
)
19
Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of
20
Mg, 91.4(1.0)ms.
The laser ion source (LIS) at the Leuven isotope separator on-line facility has been used to produce beams of exotic nuclei obtained in different types of nuclear reactions. The application of a gas ...cell filled by noble gas for thermalizing, storing and transporting trace radioactive ions and atoms, has been studied in off- and on-line conditions. Two-step laser resonance ionization has been used to produce ions of stable and radioactive isotopes inside the cell of the LIS. Results from proton-induced fission on
238U and light-/heavy-ion-induced fusion reactions are presented. The interactions of ions with impurity molecules, with noble gas atoms, with electrons and with electrical fields have been investigated in order to specify the requirements for the gas cell as a source of radioactive rare isotopes for the next generation radioactive ion beam facilities.
Optical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements and ...theoretical modelling can be performed to high precision, taking into account relativistic effects that scale approximately as the square of the atomic number. However, for the transfermium elements (those with atomic numbers greater than 100), the atomic structure is experimentally unknown. These radioactive elements are produced in nuclear fusion reactions at rates of only a few atoms per second at most and must be studied immediately following their production, which has so far precluded their optical spectroscopy. Here we report laser resonance ionization spectroscopy of nobelium (No; atomic number 102) in single-atom-at-a-time quantities, in which we identify the ground-state transition
S
P
. By combining this result with data from an observed Rydberg series, we obtain an upper limit for the ionization potential of nobelium. These accurate results from direct laser excitations of outer-shell electrons cannot be achieved using state-of-the-art relativistic many-body calculations that include quantum electrodynamic effects, owing to large uncertainties in the modelled transition energies of the complex systems under consideration. Our work opens the door to high-precision measurements of various atomic and nuclear properties of elements heavier than nobelium, and motivates future theoretical work.
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