Yrast structure of 97Zr

The yrast structure of the neutron-rich nucleus 97Zr has been studied using fission of target-like products in the reaction of a 48Ca beam on a thick 238U target. The level scheme known from the previous studies up to an energy and spin of approx. 4619 keV and 23/2-, respectively, has been extended by about 3 MeV and a few units of angular momentum. The located structure can be discussed in terms of shell model configurations

Yrast structure of Zr97 and β decay of the 27/2- high-spin isomer in Y97

The yrast structure of the neutron-rich nucleus Zr97 has been studied using fission of targetlike products in the reaction of a Ca48 beam on a thick U238 target. The level scheme, known from previous studies up to an excitation energy and spin-parity of approximately 4619 keV and 23/2-, has been extended by about 3 MeV and a few units of angular momentum. Two states fed in the β decay of the 27/2- high-spin isomer in Y97 were identified at 5570 and 5606 keV. The located level structure can be discussed in terms of shell-model configurations

Charged particle decay of hot and rotating 88^{88}Mo nuclei in fusion-evaporation reactions

A study of fusion-evaporation and (partly) fusion-fission channels for the $^{88}$Mo compound nucleus, produced at different excitation energies in the reaction $^{48}$Ti + $^{40}$Ca at 300, 450 and 600 MeV beam energies, is presented. Fusion-evaporation and fusion-fission cross sections have been extracted and compared with the existing systematics. Experimental data concerning light charged particles have been compared with the prediction of the statistical model in its implementation in the Gemini++ code, well suited even for high spin systems, in order to tune the main model parameters in a mass region not abundantly covered by exclusive experimental data. Multiplicities for light charged particles emitted in fusion evaporation events are also presented. Some discrepancies with respect to the prediction of the statistical model have been found for forward emitted $\alpha$-particles; they may be due both to pre-equilibrium emission and to reaction channels (such as Deep Inelastic Collisions, QuasiFission/QuasiFusion) different from the compound nucleus formation.Comment: 14 pages, 14 figure

Lifetime measurements of short-lived excited states, and shape changes in As 69 and Ge 66 nuclei

Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈70, N≈Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in As69 and Ge66 nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in As69 and Ge66 have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the S32(95MeV)+0.8mg/cm2 Ca40 fusion-evaporation reaction. The strongest reaction channels 3p and α2p led to the As69 and Ge66 final nuclei, respectively. Using γ-γ-recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In As69, the extracted lifetimes are τ=72 (-32, +45) fs for the 33/2+ state at 7897 keV and τ<85 fs for the 37/2+ state at 9820 keV. For the Ge66 case, the lifetime of the 11- state at 7130 keV is τ=122(±41) fs. Lifetimes in As69 and Ge66 reported in this paper have been measured for the first time in the present experiment. Conclusions: The results are discussed in the terms of deformation and shape evolution in As69 and Ge66. The quadrupole moments deduced from the measured lifetimes were compared with the cranked Woods-Saxon-Strutinsky calculations by means of the total Routhian surface method. It turns out that Band 3 in As69 shows an oblate-prolate shape transition, and above spin 33/2+ it corresponds to a prolate collective structure with β2≈0.27 and γ≈20. In turn, in Ge66 the negative-parity band built on the 7- state at 4205 keV corresponds to a triaxial shape with β2=0.33 and γ=31. Analysis of the transitional quadrupole moments derived from the experimental and theoretical ones points to a significant change of deformation in the As69 and Ge66 nuclei with increasing rotational frequency

Nuclear Structure Study of 104^{104}Pd by Coulomb Excitation at the Warsaw Heavy Ion Laboratory

International audienc

M4 RESONANCES IN LIGHT NUCLEI STUDIED AT CCB

M4 resonances in light nuclei result from the p3/2 → d5/2 stretched excitations. Their configurations should be relatively simple, which makes them good benchmarks for the theoretical calculations taking into account the role of continuum couplings. The first experimental studies aiming at tracing the decay of the M4 stretched resonance in 13C, located at 21.47 MeV, were undertaken at the Cyclotron Centre Bronowice at the Institute of Nuclear Physics Polish Academy of Sciences in Kraków, Poland (IFJ PAN). They provided information on the proton and neutron decay channels of this resonance to 12B and 12C daughter nuclei, respectively. These experimental results were then compared with the theoretical calculations based on the Gamow Shell Model approach, in terms of energy, width, and in particular, the decay pattern. Furthermore, the studies of the next cases, namely, 14N and 16O, where several M4 resonances appear at around 20 MeV, have been recently performed at CCB. The new experimental findings will serve as a testing ground for future calculations describing the heavier nuclei in this important region of the nuclear chart.</p

Coulomb excitation studies at LNL with the SPIDER-GALILEO set-up

Low-energy Coulomb excitation is one of the simplest and most known tools to study the nuclear shape; for this reason it is nowadays widely used at radioactive beam facilities. The Selective Production of Exotic Species (SPES) facility, for the acceleration of radioactive beams will soon provide the first exotic beams at the Laboratori Nazionali di Legnaro (LNL) in Italy. To this end a new particle detector (Silicon PIe DEtectoR) to be used for Coulomb excitation studies has been installed at LNL. SPIDER has been coupled to the GALILEO array of germanium detectors, and a number of experiments have been already successfully performed. This paves the way for future experiments with the radioactive beams provided by the SPES facility

Multi-step Coulomb excitation of 132Ba at HIL, Warsaw

599-601To determine the shape of 132Ba Coulomb excitation measurement has been performed at U-200P cyclotron at Heavy Ion Laboratory, University of Warsaw, Poland. A 32S beam of ~90 MeV energy has been bombarded on enriched 132Ba-target to Coulomb excite the latter nuclei. EAGLE gamma-ray spectrometer consisting of 15 single crystal HPGe detectors has been used to detect the deexcited gamma-rays from Coulomb excited Ba nuclei. The data has been collected using Particle-gamma coincidence technique for a period of seven days. The back scattered projectiles have been identified with 48 PiN diodes of 0.5 X 0.5 cm2 active area mounted in a scattering chamber of ~5 cm radius called as ‘Munich chamber’. The energy states up to ~1127 keV energy have been populated in the interested 132Ba isotope. The preliminary results of the data analysis are presented here