D. R . Napoli

Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Faculty Member

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Lifetimes of triaxial superdeformed states in 163Lu and 164Lu

The European Physical Journal A, 2002

Lifetimes of states in the yrast superdeformed bands of 163 Lu and 164 Lu were determined in a Do... more Lifetimes of states in the yrast superdeformed bands of 163 Lu and 164 Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average transition quadrupole moments, Qt = 8.2 +1.0 −0.6 b and 7.1 +0.5 −0.6 b, were deduced for one of the bands in 163 Lu and 164 Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in 163 Yb, Qt = 4.9 +1.3 −0.4 b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands correspond to a local potential energy minimum with a pronounced triaxiality, γ ∼ 20 • .

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Spectroscopy at N=Z with EUROBALL III

AIP Conference Proceedings, 1999

A complete study of the nuclear structure by means of gamma spectroscopy requires, in addition to... more A complete study of the nuclear structure by means of gamma spectroscopy requires, in addition to the high resolution gamma measurement and accurate DCO's or angular distributions, the information concerning the Electric or Magnetic character of the transition. This information for transitions in nuclei far from stability valley is now reachable in the new generation of Ge-arrays based in composite detectors. EUROBALL III is a good example with the high polarization sensitivity of the 90° ring of Clovers. The Polarization correlations PCO's measured in coincidence with the Cluster detectors permits to investigate transitions in weakly populated nuclei. In this contribution we present results on medium mass N=Z nuclei measured with EUROBALL III coupled with light particle ancillary detectors.

Subbarrier Fusion of O-16+CD-112 - Cross-Sections and Mean Angular Momenta (Vol 578, PG 374, 1994)

ABSTRACT

Signature inversion in pi i(13/2) circle times vi(13/2) structure in Ir-178

Investigations of 159–163Dy using incomplete fusion reactions

Progress in Particle and Nuclear Physics, 2001

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Elastic scattering of 58Ni+64Ni near the Coulomb barrier

Physics Letters B, 1990

Elastic scattering angular distributions have been measured for ~SNi+64Ni at three energies aroun... more Elastic scattering angular distributions have been measured for ~SNi+64Ni at three energies around the Coulomb barrier employing a new kinematic coincidence technique. The data are compared with the results of coupled-channels calculations including inelastic excitations as well as one-and two-neutron transfer reactions. The agreement is good and the calculations also agree well with the available transfer and fusion reaction data.

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Multinucleon transfer reactions in the 40Ca+124Sn system studied via γ-particle coincidences

Physical Review C, 2000

ABSTRACT

Identification of theN=79147Er nucleus throughγ-recoil coincidences

Zeitschrift für Physik A Hadrons and Nuclei, 1992

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$Research paper thumbnail of Shape isomerism and shape coexistence effects on the Coulomb energy differences in the N=Z nucleus ^{66}As and neighboring T=1 multiplets$

Shape isomerism and shape coexistence effects on the Coulomb energy differences in the N=Z nucleus ^{66}As and neighboring T=1 multiplets

Physical Review C, 2012

ABSTRACT Excited states of the N=Z=33 nucleus 66As have been populated in a fusion-evaporation re... more ABSTRACT Excited states of the N=Z=33 nucleus 66As have been populated in a fusion-evaporation reaction and studied using γ-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the T=1 states. A new 3+ isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the T=1 states with their analog partners. The unusual behavior of the Coulomb energy differences in the A=70 mass region is explained through different shape components (oblate and prolate) within the members of the same isospin multiplets. This breaking of the isospin symmetry is attributed to the correlations induced by the Coulomb interaction.

Extreme nuclear deformations studied at the GASP spectrometer

Acta Physica Hungarica A) Heavy Ion Physics, 1997

Very exotic shapes can be assumed for the nuclei at high angular momenta. Their study has become ... more Very exotic shapes can be assumed for the nuclei at high angular momenta. Their study has become possible with the advent of the last generation high-resolution γ-ray spectrometers. In this talk results are presented on superdeformed nuclei of theA=140 mass region where a detailed spectroscopy in the second minimum is now possible. Hyperdeformed rotational bands, expected in the third minimum, lie at even higher spins where their observation is very difficult from the experimental point of view. We have up to now only weak signals of their presence. The status of the search for hyperdeformation in152Dy is reported.

Fusion and Quasi-Elastic Reactions at Near-Barrier Energies

NATO ASI Series, 1994

The recent availability of high precision data of heavy-ion fusion and quasi-elastic reactions at... more The recent availability of high precision data of heavy-ion fusion and quasi-elastic reactions at energies close to the Coulomb barrier allows detailed comparisons with microscopic nuclear theories. Two experiments have been recently performed in Legnaro: A) the detailed measurement of the fusion excitation function for the system 58Ni+60Ni and B) the measurement of the elastic scattering and transfer cross sections for 32S+208Pb. Both experiments have the common aim of enlightening the role of nucleon correlations, in the fusion process (A) and in the multinucleon transfer (B). In the following a very short preliminary report is given.

Electromagnetic transition strengths in 33 S

Journal of Physics: Conference Series, 2014

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Mars - a Novel Γ-Ray Detector Array

Nuclear Structure, 2001

The status of the MARS project to build a gamma-ray tracking array is presented. It comprises the... more

Author's personal copy HPGe detectors long time behaviour in high-resolution g spectrometry

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

a b s t r a c t A large set of data on long term performance of n-type HPGe detectors used in GAS... more a b s t r a c t A large set of data on long term performance of n-type HPGe detectors used in GASP, EUROBALL and CLARA g spectrometers, as well as environmental measurements have been collected over two decades. In this paper a detailed statistical analysis of this data is given and detector long term behaviour is provided to the scientific community. We include failure, failure mode, repair frequency, repair outcome and its influence in the energy efficiency and energy resolution. A remarkable result is that the life span distribution is exponential. A detector's failure is a memory-less process, where a previous failure does not influence the upcoming one. Repaired spectrometers result in high reliability with deep implications in the management of large scale high-resolution gamma spectrometry related projects. Findings show that on average, detectors initial counting efficiency is slightly lower ($ 2%) than that reported by the manufacturers and the repair process (including...

$Research paper thumbnail of Decay-out of the yrast highly-deformed band in $^{{136}Nd$}:towards an experimental extraction of the neutron pairing gap in the second well$

Decay-out of the yrast highly-deformed band in $^{{136}Nd$}:towards an experimental extraction of the neutron pairing gap in the second well

Lifetime Measurements in 67SE and 67AS Mirror Pair: A Test of Isospin Symmetry Breaking

Changing Facets of Nuclear Structure, 2008

The comparison of analogue E1 transitions of mirror nuclei offers a valuable tool in the investig... more The comparison of analogue E1 transitions of mirror nuclei offers a valuable tool in the investigation of isospin symmetry breaking. Differences in the measured B(E1) reduced strengths in fact can be interpreted as the signature of isospin mixing. In this work, the isospin Tz = 1/2 nuclei 67As and 67Se were investigated. The nuclei were produced via the fusion evaporation

Probing core polarization around Ni-78: intermediate energy Coulomb excitation of Ni-74

Heavy Ion Accelerator Symposium 2013, 2013

The study of the evolution of nuclear shells far from stability provides fundamental information ... more The study of the evolution of nuclear shells far from stability provides fundamental information about the shape and symmetry of the nuclear mean field. Nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Of particular interest is the region of 78 Ni where the large neutron excess coincides with a double shell closure. We have recently measured the B(E2; 0 + → 2 +) of the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory of the Michigan State University. The 74 Ni secondary beam has been produced by fragmentation of 86 Kr at 140 AMeV on a thick Be target. Selected radioactive fragments impinged on a secondary 197 Au target where the measurement of the emitted γ-rays allows to extract the Coulomb excitation cross section and related structure information. Preliminary B(E2) values do not point towards an enhancement of the transition matrix element and the comparison to what was already measured by Aoi and co-workers in [1] opens new scenarios in the interpretation of the shell evolution of the Z=28 isotopes.

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Alpha-cluster states populated in 24Mg + 12C

Charged particle and γ-decays in light α-like nuclei are investigated for 24 Mg+ 12 C. Various th... more Charged particle and γ-decays in light α-like nuclei are investigated for 24 Mg+ 12 C. Various theoretical predictions for the occurence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are presented. The inverse kinematics reaction 24 Mg+ 12 C is studied at E lab (24 Mg) = 130 MeV. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. Coincident events from α-transfer channels were selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on 20 Ne-γ and 16 O-γ coincidences.

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Reaction mechanisms in 24Mg+ 12C and 32S+ 24Mg

Decay Out of the Yrast and Excited Highly Deformed Bands in the Even-Even Nucleus134Nd

Physical Review Letters, 1996

The decay out of the yrast and excited highly deformed (HD) bands in 134 Nd has been investigated... more The decay out of the yrast and excited highly deformed (HD) bands in 134 Nd has been investigated via the 28 Si 1 110 Pd reaction at 130 MeV using the GASP array. Several deexcitation pathways have been established for both the yrast and excited HD bands. The resulting spins remove previous ambiguities in the assignment of the excited HD band and confirm the structure assigned to the yrast HD band. The decay out is understood in terms of mixing between the normal-deformed and HD states, which is triggered by the crossing between the ni 13͞2 and nd 5͞2 orbitals. [S0031-9007(96)00639-4]

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D. R . Napoli

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