The structure of 74Se at low energy was investigated via spectroscopy of internal conversion electrons at the INFN Legnaro National Laboratories (LNL). A set of internal K-conversion coefficients and ...monopole transition strengths was measured. A large ρ2(E0;22+→21+)⋅103=210(130) value was deduced. This result, in addition to a low upper limit for the 03+→02+ electron transition, casts in doubt a simple interpretation of the 74Se low-lying structure, in particular the recently proposed spherical, vibrational character. New microscopic beyond-mean-field calculations generally agree with the experimental results and are capable of producing a large ρ2(E0;22+→21+) value, even if still a factor ≈7 smaller than the experiment. Triaxiality and a complex shape-coexistence and mixing scenario seem responsible for this unexpected experimental result.
.
An in-beam test of two pixel-type silicon detectors of the TRACE detector project has been performed at Laboratori Nazionali di Legnaro (Italy). The aim was to investigate the lowest kinetic energy ...values at which isotopic identification of heavy-ion reactions products with mass
A
∼
10
is possible, by using a single-layer silicon detector. Two separate read-out chains, analog and digital, were used, and the Pulse Shape Analysis technique was employed to obtain the particle identification matrices for the digitally processed data. The results confirmed the high capability of the Pulse Shape Analysis method which can be used for light ion identification, with performances similar to the analog approach. Separation in both charge and mass was obtained for Li and Be isotopes, however, the presence of a significant background from alpha particles severely limited the data analysis in the lower energy region. Due to this effect, the identification of the light products (
7, 6
Li isotopes) could be possible down to
∼
24
.
5
MeV only, while the
9, 7
Be isotopes were separable down to
∼
29
MeV. This gives the value of
<
4
MeV/nucleon as the lowest kinetic energy for light products identification by using the pixel-type detectors of the TRACE project, in the present experimental conditions.
g factor of the 12+K-isomer in 174W Rocchini, M.; Nannini, A.; Benzoni, G. ...
The European physical journal. A, Hadrons and nuclei,
2020/11, Letnik:
56, Številka:
11
Journal Article
Recenzirano
The
g
factor of the
12
+
K
-isomer in
174
W has been measured by means of the time-differential perturbed angular distribution technique as
g
(
12
+
)
=
+
0.304
(
11
)
. In addition, the half-life of ...the isomer has been remeasured as
T
1
/
2
(
12
+
)
=
124
(
8
)
ns, in agreement with the literature value and confirming the anomalous hindrance
F
of the
E
2 transition to the
10
+
level of the ground state band with respect to the
γ
-tunnelling model prediction. The measured
g
factor has been compared with estimates based on experimental
g
factors from odd-mass isotopes in the same mass region and with Nilsson model calculations. The results establish unique features of the
12
+
K
-isomer in
174
W, which can possess a non-pure intrinsic configuration and/or can be characterised by values of the intrinsic quadrupole moment
Q
0
and the rotational
g
factor
g
R
significantly different with respect to the majority of
K
-isomers at mass
A
≈
180
.
The γ-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor ...in Grenoble. By using a highly efficient HPGe array, coincidences between γ-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 μs isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, revealed a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.
In this contribution, we report some recent progress in our understanding of particle-vibration coupling (PVC) in nuclei. In particular, we first review the formal development that has allowed some ...of us to deduce the PVC equations within the Green’s functionmethod. Applications are then discussed, both in the case of single-particle states and giant resonances in magic nuclei. We also present a new model that extends the PVC ansatz and is meant to account for the complete low-lying spectra of odd nuclei.
Recent results on the structure of 47Ca will be presented. The nucleus of interest was populated via the cold-neutron capture 46Ca(n,γ) reaction, on a rare 46Ca target, during the EXILL experimental ...campaign at the nuclear reactor of Institut Laue- Langevin in Grenoble. High-resolution γ-ray spectroscopy, performed with a composite array of HPGe detectors, enabled the identification of new transitions deexciting states between the neutron-capture level and the ground state. Experimental data will be compared with a novel microscopic theoretical model, currently under development, specifically designed to describe the low-lying structure of odd-mass nuclei with one valence particle/hole outside a spherical doubly-magic core, using the Skyrme effective interaction self-consistently.
Neutron rich nuclei around 48Ca have been measured with the CLARA–PRISMA setup, making use of 48Ca on 64Ni binary reactions, at 5.9 MeV/A. Angular distributions of γ rays give evidence, in several ...transfer channels, for a large spin alignment (≈70%) perpendicular to the reaction plane, making it possible to firmly establish spin and parities of the excited states. In the case of 49Ca, states arising from different types of particle–core couplings are, for the first time, unambiguously identified on basis of angular distribution, polarization and lifetime measurements. Shell model and particle–vibration coupling calculations are used to pin down the nature of the states. Evidence is found for the presence, in the same excitation energy region, of two types of coupled states, i.e. single particle coupled to either 48Ca or 50Ca simple configurations, and particle–vibration coupled states based on the 3− phonon of 48Ca.
The experimental setup GAMIPE used for gyro magnetic factor measurements at Laboratori Nazionali di Legnaro and a recent experimental work regarding K-isomers in 174W are described. Aim of the ...experiment is to study the detailed structure of the isomeric states wave functions, by the measurement of the magnetic dipole moments. This piece of information can provide interesting hints for theoretical models. Preliminary results concerning the population of the isomers of interest and half-lives are presented.
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