Search

The low-spin structure of one-proton, one-neutron 210Bi nucleus was investigated in cold-neutron capture reaction on 209Bi. Theγ -coincidence measurements were performed with use of EXILL array consisted of 16 HPGe detectors. The experimental results were compared to shell-model calculations involving valence particles excitations. The 210Bi nucleus offers the potential to test the effective proton-neutron interactions because most of the states should arise from the proton-neutron excitations. Additionally, it was discovered that a few states should come from the couplings of valence particles to the 3- octupole vibration in 208Pb which provides also the possibility of testing the calculations involving the core excitations. [ABSTRACT FROM AUTHOR]

The multinucleon transfer reaction 40Ar+208Pb has been measured at Elab = 260 MeV with the large solid angle magnetic spectrometer PRISMA. Mass and charge yields, differential and total cross sections, total kinetic energy loss distributions of different channels were simultaneously studied. Angular distributions were measured in a wide angular range by matching three different angular settings of the spectrometer. Absolute cross sections were obtained after the response function of the spectrometer was evaluated. These cross sections for different transfer channels allow the discussion of the role played by nucleon-nucleon correlations. [ABSTRACT FROM AUTHOR]

Applied and material physics studies with positron beams of Fermi-surfaces, defects, interfaces etc. offer excellent diagnostics tools. At ELI-NP, an intense γ beam of about 1011 photons/s with energies up to 3.5 MeV will be used to generate a positron beam via pair production in a tungsten converter target. To obtain a high intensity beam of moderated positrons the design of the positron source is of high importance. The design of a dedicated positron source at ELI-NP is being investigated based on extensive GEANT4 simulations. The goal of the simulations is to optimize the geometry of the target and the gamma beam collimation. We present here the characteristics of the positron beam obtained for different geometries of the converter target. [ABSTRACT FROM AUTHOR]

Heavy ion beams are delivered at the Laboratori Nazionali di Legnaro by the accelerator complex Tandem-ALPI-PIAVE. The Tandem XTU is a Van de Graaff accelerator normally operated at terminal voltages of up to about 15 MV. The Tandem accelerator can be operated in stand-alone mode or as an injector for the linac booster ALPI. The linear accelerator ALPI is built of superconducting resonant cavities and consists of a low-beta branch, particularly important for the acceleration of the heavier mass ions, a medium-beta branch, and a high-beta branch. ALPI can be operated also with the PIAVE injector that consists of a superconducting linac and an ECR source. The PIAVE source was mainly used for the acceleration of intense noble gas beams but most recently also a first metallic beam was delivered to the users. The accelerator complex delivers beams of ions from protons to gold in three experimental areas on 11 different beam lines. A rich scientific activity is ongoing at the Tandem-ALPI-PIAVE accelerator complex, beam time being shared between nuclear physics research and applied and interdisciplinary physics research. An overview of the present status and perspectives of the Tandem-ALPI-PIAVE complex and its physics program is given in the present paper. [ABSTRACT FROM AUTHOR]

The 14N(p,γ)15O reaction is the slowest process of the CN cycle, and thus it is of high astrophysical interest since it regulates the total rate of energy and neutrinos production through the cycle. The 14N+p ground state capture is strongly influenced by a sub-threshold resonance corresponding to the 6.79 MeV state in 15O. The width of this resonance is a major source of uncertainty in the extrapolation of the reaction cross section in the Gamow energy window. Preliminary results of a new Doppler Shift Attenuation measurement of the lifetime of the 6.79 MeV state in 15O are discussed. The level of interest was populated via the 2H(14N,n)15O reaction in inverse kinematics at 32 MeV beam energy. The gamma-rays emitted in the decay of the 6.79 MeV level to the ground state were detected with the AGATA Demonstrator array of high-purity germanium detectors. The sensitivity of the shape of the peak in the gamma-ray energy spectrum to the level lifetime is investigated comparing the experimental peaks with detailed Monte Carlo simulations of the reaction mechanisms and the gamma-ray emission and detection. Nuclear levels in 15N (also populated in the 14N+2H reaction) for which the lifetimes are known in the literature provided a test of the analysis technique. [ABSTRACT FROM AUTHOR]

The preliminary results of a new direct measurement of the lifetime of the first excited 3/2+ state in 15O are discussed. An accurate evaluation of this lifetime is of paramount importance for the determination of the cross section of the 14N(p,γ)15O reaction, the slowest one in the CNO cycle, at the energies of the solar Gamow peak. The 2H(14N,15O)n reaction in inverse kinematics at 32MeV beam energy (XTU Tandem, LNL) was used to populate the level of interest, which decays via a 6.79 MeV E1 gamma-ray transition to the ground state. Gamma rays were detected with 4 triple clusters of HPGe detectors of the AGATA Demonstrator array. The energy resolution and position sensitivity of this state-of-the-art gamma-ray spectrometer have been exploited to investigate the Doppler Shift Attenuation effect on the lineshape of the gamma-ray peak in the energy spectrum. The deconvolution of the lifetime effects from those due to the kinematics of the emitting nuclei has been performed using detailed Monte Carlo simulations of the gamma emission and detection. CDCC-CRC calculations for the nucleon transfer process have been used for this purpose and preliminary results are shown. [ABSTRACT FROM AUTHOR]

The transfer reaction for the 116Sn+60Ni system has been studied using the PRISMA magnetic spectrometer at different bombarding energies from above to well below the Coulomb barrier. The experiment has been done in inverse kinematics and light target-like ions have been detected with PRISMA placed at very forward angles. Good mass, nuclear charge and kinetic energy resolutions have been achieved. Sufficient statistics has been accumulated to extract angular distributions for different bombarding energies have been extracted and the response function of the spectrometer has been studied to correct for the aberration due to the transport of the ions in PRISMA. The comparison between the present case and the previously measured 96Zr+40Ca system, superfluid and near closed shells nuclei, respectively, should significantly improve our understanding of nucleon-nucleon correlation properties in multinucleon transfer processes. [ABSTRACT FROM AUTHOR]

Binary reactions at energies close to the Coulomb barrier received recently a significant boost thanks to the advent of the large solid angle magnetic spectrometer PRISMA coupled to the γ array CLARA. In the present paper different aspects of the recent results of nuclear structure and reaction dynamics will be presented, focusing more closely on the reaction mechanism. [ABSTRACT FROM AUTHOR]

The lifetimes of excited states of the 122Ba ground—state band, populated via the 108Cd(16O,2n)122Ba and the 112Sn(13C,2n)122Ba reactions, have been measured using the Recoil Distance Doppler—Shift method. The level scheme of 122Ba has also been revised. [ABSTRACT FROM AUTHOR]

Medium and high spin states of the nuclei close to the N = 50 shell closure are investigated using deep inelastic and multi-nucleon transfer reactions. New excited states of the nuclei 81Ga, 82Ge and 83As at N = 50 shell closure have been identified by means of the 82Se+238U reaction. Gamma rays have been acquired using the PRISMA-CLARA setup of the Laboratori Nazionali di Legnaro, Italy (LNL). [ABSTRACT FROM AUTHOR]

Recent experimental and theoretical advances have been achieved in the field of multinucleon transfer reactions among heavy-ions. Detailed A,Z and Q-value distributions allow to identify the relevant degrees of freedom acting in the transfer process. The advent of the large solid angle magnetic spectrometer PRISMA coupled to the large γ-array CLARA was a major experimental breakthrough, as reaction mechanism and nuclear structure studies of neutron-rich nuclei can be performed via γ-particle coincidences. Examples of recent studies, mainly focused on the reaction mechanism, are presented. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The present work takes advantage of the multinucleon transfer mechanism between heavy reaction partners to study the population pattern of excited nuclear states in near spherical Zirconium isotopes following the 90Zr + 208Pb reaction at an energy closed to the Coulomb barrier. Both the projectile and the target are well known closed shell nuclei offering an optimum situation for clean experimental and theoretical conditions. Total kinetic energy loss (TKEL) distributions were compared with calculations performed with the GRAZING code. The ability to use the TKEL as a selection tool for the states at different excitation energies was shown. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This contribution reports on the results of an experiment to study the near-yrast states in selenium- and osmium-like nuclei, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. The experimental results for the level scheme for 84Se are presented together with investigations into the use of multi-dimensional gamma-ray energy gating to investigate angular momentum population in such heavy-ion binary reactions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Deep-inelastic and multi-nucleon transfer reactions can be used to populate nuclei with relatively large neutron excess. Recently, at the Laboratori Nazionali di Legnaro, a setup consisting on an efficient γ-ray detection system CLARA coupled to the large acceptance magnetic spectrometer PRISMA, capable of tracking the trajectories of the reaction products, has been assembled. During the first year of activity, the experiments performed with the CLARA-PRISMA setup, have been focused mainly on the nuclear structure of neutron-rich nuclei. In particular, nuclei around N=20, N=50 and lying in the A∼60 transitional region with N<40, have been investigated. In this contribution, results of these experiments will be reported. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The energy spectra and relative transition rates of 176,178,180Os were found to be very similar to the values calculated in the framework of the critical point symmetry X(5). In order to enable more stringent tests, including also absolute transition probabilities, two coincidence RDDS lifetime measurements were performed at the Laboratori Nazionali di Legnaro with the GASP spectrometer using the 152,154Sm(29Si,5n)176,178Os reactions. The deduced transition quadrupole moments in 178Os agree well with the X(5) predictions. For 176Os only preliminary results were obtained so far. These preliminary data support an X(5) like structure also in the case of 176Os. The experimental data of both nuclei are compared to calculations in the framework of the interacting boson model (IBM) and of the general collective model (GCM). © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Spectroscopic quadrupole moment measurements for high-spin isomeric states in 192,193,194Pb nuclei have been performed by the time-differential perturbed γ-ray angular distribution method. The quadrupole moments of the isomers described by quasineutron configurations in neutron-deficient Pb nuclei are well reproduced by the pairing plus quadrupole model, which predicts for these states a very small prolate deformation β2 ≈0.02. The quadrupole moment of the 11- isomeric state in 192Pb involving the π(3s1/2-2 1h9/2 1i13/2) configuration corresponds to a deformation β2=-0.11(1). The quadrupole moments of the proton intruder states in Pb nuclei are compared with theoretical predictions of tilted-axis cranking, mean-field and interacting boson models. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This contribution reports on the results of an experiment to study the near-yrast states in selenium isotopes around N=50, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. Discrete decays from states with spins of 20h and higher are clearly identified in the Os-like fragments. Information on the size of the energy gap between the f5/2 and p3/2 proton orbitals can be inferred from the spectroscopy of the N=48 isotone, 82Se. The experiment results for the level schemes for 80,82Se derived in the current work are compared with restricted-basis shell model calculations, which give a good description of the yrast sequences of these nuclei using a basis space limited to excitations in the (p3/2 , p1/2 , g9/2 ) neutron and (f5/2 , p3/2 , p1/2 ) proton orbitals. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Excited states have been studied in sd-shell nuclei following the 16O (70 MeV) + 24Mg (400 μg/cm2) fusion-evaporation reaction. The GASP spectrometer in conjunction with the charged-particle detector ISIS and the Neutron ring allowed the detection of the γ-rays in coincidence with evaporated light particles. New data on the mirror pairs A=31 and A=35 have been obtained. In particular, the comparison between the level schemes of 35Ar and 35Cl has confirmed the importance of the electromagnetic spin-orbit term, which explains the large Mirror Energy Difference values. Evidence of isospin mixing can be deduced from the E1 transitions. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have studied the high spin states in 160–162Ho in order to investigate the properties of the rotational bands and their dependence on the single particle orbits involved. The reaction 158,160Gd(7Li,xn) at 56 MeV were used to produce the Ho isotopes of interest. In all three Ho isotopes the known rotational bands have been significantly extended. New band-crossings have been observed for the first time in this work. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have studied the γ-decay properties of 21Ne up to the limits of the particle emission thresholds in order to establish the band structure. The GASP γ-ray detector array together with the multi-detector array, ISIS, were used for the selection of the reaction channels. The reaction 16O(7Li,pn)21Ne has been studied at E=29 MeV. The observed decays in 21Ne, support the identification of parity doublets with states of opposite parity connected by strong dipole transitions. The behaviour of the octupole deformed bands in 21Ne is interpreted as consisting of an intrinsic reflection asymmetric (4He+16O)-structure with an additional valence neutron in σ- and π-orbitals. Using the same experimental set-up the emission of the light unbound cluster 8Be has been studied in the reaction 18O+13C→31Si→23Ne+8Be. The emission has been studied relative to the sequential emission of 2α-particles. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The feasibility of the entire process of γ-ray tracking is demonstrated experimentally for the first time. The accurracy of the results is verified by the capability to carry out Doppler correction of γ-rays emitted in flight. The resolution of the 847.8 keV transition detected with the MARS detector after Coulomb excitation of a [sup 56]Fe beam could be improved from 15 keV to below 5 keV (FWHM). [ABSTRACT FROM AUTHOR]

Recent experimental and shell model studies of isospin symmetry along the ground state rotational bands in the mirror nuclei [sup 50]Fe and [sup 50]Cr are presented. This is the heaviest T=1 mirror pair studied so far at high spin. It is shown that the Coulomb energy differences provide a good tool to probe the alignment mechanism at the backbending and that they also give information about the evolution of yrast radii as a function of the angular momentum. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Lifetimes of high-spin states in 69As have been measured using Doppler shift attenuation technique with the GASP and RFD setup. The determined transition probabilities indicate large deformation associated with some rotational bands in this nucleus. [ABSTRACT FROM AUTHOR]

Recently, an intense experimental effort has been devoted to the search of empirical proofs of critical-point symmetries in nuclear structure. These symmetries describe shape-phase transitions and provide parameter-free predictions (up to over-all scale factors) for excitation spectra and B(E2) values. This contribution reports on recent plunger-lifetime measurements ON 102Pd carried out at LNL, Legnaro, with the Cologne plunger apparatus coupled to the GASP spectrometer and using the 92Zr(13C,3n)102Pd reaction at 48 MeV. According to the results of our measurements, 102Pd is so far the best known paradigm of the E(5) critical-point symmetry. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The transition strenghts for the low—lying levels of 122,124Ba have been determined analysing the Recoil Distance Doppler Shift data by the Differential Decay Curve Method. The trend of normalised B(E2) reveals a drop in correspondance of the 81+ state. This feature is also present in 122Ba: entering the backbending region the interplay between collective and quasiparticle degrees of freedom have to be carefully taken into account. [ABSTRACT FROM AUTHOR]