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A new superdeformed band has been discovered in a EUROBALL experiment and assigned to 143Eu. It has a maximum intensity of 35% of the 143Eu yrast superdeformed band and the transition energies of the two bands are very similar. Based on comparison with cranked shell model calculations the new band is tentatively assigned the high- N intruder configuration π62ν70 and the parity and signature quantum numbers (π,α) = (−1,+1/2). In addition to the already known high-energy transition at 3361 keV another discrete line at 2715 keV was found to be in coincidence with the yrast superdeformed band. However, it was not possible to connect the decay out of either of the superdeformed bands to known normally deformed states. [ABSTRACT FROM AUTHOR]

Excited states in the Tz= 0 nucleus 70Br have been investigated using the reaction 58Ni(16O,1 p3 n). γ rays were detected with one EUROBALL CLUSTER detector and three single HPGe detectors. Charged particles and neutrons were registered with the Rossendorf silicon ball and six modules of the EUROBALL neutron wall, respectively. The identification of γ transitions in 70Br is based on the analysis of γγ-proton-neutron coincidences. A level scheme of 70Br has been established for the first time. It shows a multiplet-like structure of probably isospin T= 0 while T= 1 isobaric analogue states are not observed. [ABSTRACT FROM AUTHOR]

The high energy γ-ray emission accompanying the spontaneous fission of 252Cf has been measured in coincidence with individual fission fragments selected by discrete γ-ray transitions. The enhancement of the γ-ray emission probability in the energy range Eγ= 3–8 MeV has been observed for the fission fragments in the region of nearly symmetric mass splitting, confirming results reported in previous investigations. The γ-γ coincidence technique employed in the present work clearly demonstrate that the major contribution to this enhancement is caused by the fission channels where one fragment is near to the N= 82 or Z= 50 shell closures. The high energy γ-ray emission probability does not show any significant dependence on the number of neutrons emitted in the fission process, supporting the hypothesis that high energy γ-rays are mainly emitted from the fragments after the neutron evaporation. [ABSTRACT FROM AUTHOR]

Pure elastic and inelastic scattering cross sections have been measured for the systems 58Ni +90,94Zr at energies near the Coulomb barrier where not only quasi-elastic and fusion but also deep-inelastic process come into play. Coupled channels calculations including both projectile and target inelastic excitations can successfully explain the elastic and inelastic scattering angular distributions with an energy-independent semi-empirical bare potential. The calculation reproduces also the sum of the total quasi-elastic, fusion and deep-inelastic cross sections. [ABSTRACT FROM AUTHOR]

High-spin states in 45Sc, 45Ti and 43Ca were studied by means of multiple γ- and γ-recoil-coincidences with the use of the GASP array and the Recoil Mass Spectrometer. The nuclei were populated in the 60 MeV 18O +30Si reaction. For the DSAM lifetime measurement the 35Cl +12C reversed kinematics reaction was used. In the article, a complete description of the experimental techniques used in course of the performed experiments is presented. The level schemes and the detailed information on the observed state properties, including B(M1) and B(E2) transition rates are inserted as well as their shell model interpretation. [ABSTRACT FROM AUTHOR]

The even-even nucleus 128Nd was studied via in-beam γ-ray spectroscopy using the 40Ca + 82Mo reaction at 190 MeV. Two new bands were observed besides the yrast one, that has been extended up to spin 34+. Configurations were assigned to the three bands by analysing their rotational properties and by comparison with the neighboring even-even nuclei. [ABSTRACT FROM AUTHOR]

The even-even nucleus 122Ba was studied via in-beam γ-ray spectroscopy using the 40Ca + 92Mo reaction at 190 MeV. Five bands were observed, four more that can be found in the literature. Configurations were assigned to the various bands from the comparison with the neighboring even-even nuclei. [ABSTRACT FROM AUTHOR]

High spin states in 128Ba have been investigated with the fusion–evaporation reaction 96Zr(36S,4n)128Ba at a beam energy of 150 MeV with the GASP-spectrometer at INFN in Legnaro, Italy. The level scheme could be extended to higher spins and six-quasiparticle states have been observed. The deduced alignments are compared to the predictions of previously reported cranked shell model calculations. [ABSTRACT FROM AUTHOR]

The 178Pt and 181Au nuclei have been studied with the (230 MeV) 46Ti +142Nd fusion-evaporation reaction; γ-rays, evaporated particles and recoiling nuclei have been detected by the γ-array GASP + the Si ball ISIS + the recoil mass spectrometer RMS. The newly observed structures in 178Pt and 181Au are most probably built on the proton and quasi-proton h9/2 and i13/2 configurations. [ABSTRACT FROM AUTHOR]

High spin states in 127Ba have been investigated with the fusion–evaporation reaction 96Zr(36S,5n)127Ba at a beam energy of 150 MeV with the GASP-spectrometer at INFN in Legnaro, Italy. The level scheme could be extended to high spins resulting in the observation of five-quasiparticle states. Altogether 15 band structures were placed in the level scheme. [ABSTRACT FROM AUTHOR]

Prompt and delayed γ-rays in nuclei of the 208Pb region produced in 450 MeV 76Ge +208Pb collisions have been studied at GASP. Yrast states above the α-decaying isomer in 211Po have been located including a 0.25 μs 31/2− isomer at 2135 keV and a 2 μs isomer at 4874 keV. [ABSTRACT FROM AUTHOR]

The nucleus 84Nb has been studied with the 58Ni(28Si,pnγ) reaction at 90 MeV. Several rotational structures are established and connected to an irregular low-energy level scheme which includes one isomeric level whose decay was observed before. [ABSTRACT FROM AUTHOR]

The structure of Sn has been investigated through the Cr(Ni,2pn) reaction at a beam energy of 210 MeV. In addition to an extension of the spherical level scheme, a regular sequence of dipole transitions has been found. The experimental results are in agreement with the prediction of Tilted Axis Cranking calculations, which satisfactorily explain the properties of the band. [ABSTRACT FROM AUTHOR]

Abstract: The γ decay of the yrast trap in 52Fe has been measured for the first time. The two E4 γ-branches to the states are hindered with respect to other reduced transition probabilities measured in the shell. The interpretation of the data is given in the full pf shell model framework, comparing the results obtained with different residual interactions. It is shown that measurements of hexadecapole transition probabilities constitute a powerful tool in discriminating the correct configuration of the involved wavefunctions. [Copyright &y& Elsevier]

Abstract The GALILEO array is a high-efficiency γ -ray spectrometer, resident at the Legnaro National Laboratory (LNL)in Italy, and it is currently used in combination with the Si-ball EUCLIDES for the detection of charged-particles. The combined setup was used in the 6 Li+89Y experiment with incident energies of 22 MeV and 34 MeV to investigate the influence of breakup and transfer of weakly bound projectile on the fusion process. Using the coincidence by the charged particles and γ -rays, the different reaction channels can be clearly identified and the different reaction mechanisms can be clearly studied. It is shown that this facility can be used well to explore the fusion reaction mechanisms induced by weakly bound nuclei. [ABSTRACT FROM AUTHOR]

We report the evidence for irreversible changes in the conductivity, σ ( T ) , of a-Ge 3 N x ( 3.7 < x < 4.6 ) and quasi-stoichiometric a-Ge 2 O y N x thin films occurring at T ≳ 630 K , under high vacuum conditions. We have found that σ ( T ) curves not only depend on the material properties but also on the thermal history undertaken by films. The irreversibility in σ ( T ) , during heating in vacuum, is correlated to the transformation of the native GeO 2 into volatile GeO. Thermal annealing in N 2 atmosphere, on the contrary, results to extend film stability up to 973 K. At higher T , domes and pits are formed onto the film surface, due to the strong effusion of N-rich volatile species. Unstable N-Ge bonds can explain both the nitrogen thermodynamic instability and the Ge nano-crystallisation process occurring in a-Ge 3 N x films, upon heating until 1023 K. Compared to a-Ge 3 N x , quasi-stoichiometric a-Ge 2 O y N x is both more insulating and more stable upon heating up to 1023 K under N 2 flow, that makes it a suitable passivating layer material for the fabrication of electronic devices. [ABSTRACT FROM AUTHOR]

This work reports a detailed investigation of the properties of germanium nitride and oxynitride films to be applied as passivation layers to Ge radiation detectors. All the samples were deposited at room temperature by reactive RF magnetron sputtering. A strong correlation was found between the deposition parameters, such as deposition rate, substrate bias and atmosphere composition, and the oxygen and nitrogen content in the film matrix. We found that all the films were very poorly crystallized, consisting of very small Ge nitride and oxynitride nanocrystallites, and electrically insulating, with the resistivity changing from three to six orders of magnitude as a function of temperature. A preliminary test of these films as passivation layers was successfully performed by depositing a germanium nitride film on the intrinsic surface of a high-purity germanium (HPGe) diode and measuring the improved performance, in terms of leakage current, with respect to a reference passivated diode. All these interesting results allow us to envisage the application of this coating technology to the surface passivation of germanium-based radiation detectors. [ABSTRACT FROM AUTHOR]

Electrical conductivity, σ ( T ), of a-Ge 3 N x (3.7 < x < 4.6) and quasi-stoichiometric a-Ge 2 O y N x films has been investigated as a function of the temperature. Layers present a highly insulating behavior with conductivity and thermal activation energy rapidly rising, increasing T from room temperature to 600 K. Depending on the film composition, the conductivity can vary up to six orders of magnitude. Data analysis of σ ( T ) revealed a clear relation between the pre-exponential factor and the thermal activation energy, suggesting the validity of the Meyer-Neldel rule. For all investigated films, typical Meyer-Neldel parameters assume values in a narrow range: 10 −8 < σ 00 < 10 −6 ( Ω cm) −1 and 41 < E MN < 51 meV. To account for this behavior we have considered a model based on a statistical shift of the Fermi level upon the temperature raise. Our study is the first experimental evidence of this kind of electrical behavior in this class of materials. [ABSTRACT FROM AUTHOR]

Aiming at the production of HPGe diodes for γ-ray detection, surface passivation of the pristine Germanium surface is pursued by treatment of freshly etched, highly reactive Ge (100) surface by different chemicals, to obtain chemisorbed species with sufficient insulating properties for allowing high voltage application (up to 1100 V) with low leakage currents (lower than 30 pA). (100) surface termination of Ge crystal with hydride, methoxide, and sulphide is carried out by wet chemical treatments using suitable reactants. The chemical composition of the newly formed monolayers is investigated with regards to the nature of chemical bonding with Ge atop atoms. To this aim Fourier Transform Infrared Spectrometry (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were used; the performance as dielectric layer of each native Ge compound/complex is measured directly from I–V measurements of a HPGe diode. Atomic stability of each surface layer is monitored detecting structural changes after air exposure by XPS and FTIR spectroscopies and by relevant leakage current variations. [ABSTRACT FROM AUTHOR]

Abstract: A large set of data on long term performance of n-type HPGe detectors used in GASP, EUROBALL and CLARA γ 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 annealing) does not affect significantly the energy efficiency, even after a long period of use. Repaired detector energy resolution statistics show that the probability, that a repaired detector will be at least as good as it was originally, is more than 3/4. [Copyright &y& Elsevier]

Abstract: Products of 130Te+275 MeV 64Ni and 208Pb+345 MeV 58Ni collisions at energies slightly above the Coulomb barrier have been studied in two gamma spectroscopy thick target experiments. The product yield distributions have been established from the coincidence analysis supplemented by target radioactivity measurements. Neutron evaporation from excited primary products has been estimated to determine the pre-emission maps of fragments. The transfer of protons and neutrons between the colliding ions is discussed in terms of the ratio equilibration. The discussion of experimental values compared with expectations based on potential energy minimizations leads to conclusion that the involved nuclei are dynamically deformed during the crucial interaction time. These results are discussed in connection with the earlier published study of the 208Pb+350 MeV 64Ni system . The present and perspective use of deep-inelastic reactions for spectroscopic studies of exotic neutron-rich nuclei in experiments with stable and radioactive beams is outlined. [Copyright &y& Elsevier]

Excited states in 56Zn were populated following one-neutron removal from a 57Zn beam impinging on a Be target at intermediate energies in an experiment conducted at the Radioactive Isotope Beam Factory at RIKEN. Three γ rays were observed and tentatively assigned to the 6 + → 4 + → 2 + → 0 + yrast sequence. This turns 56Zn into the heaviest T z = − 2 nucleus in which excited states are known. The excitation-energy differences between these levels and the isobaric analogue states in the T z = + 2 mirror partner, 56Fe, are compared with large-scale shell-model calculations considering the full pf valence space and various isospin-breaking contributions. This comparison, together with an analysis of the mirror energy differences in the A = 58 , T z = ± 1 pair 58Zn and 58Ni, provides valuable information with respect to the size of the monopole radial and the isovector multipole isospin-breaking terms in the region above doubly-magic 56Ni. [ABSTRACT FROM AUTHOR]

A sequence of excited states has been established for the first time in the proton-rich nucleus 48Fe (Z=26, N=22). The technique of mirrored (i.e. analogue) one-nucleon knockout reactions was applied, in which the T z = ±2 mirror pair, 48Fe/48Ti were populated via one-neutron/one-proton knockout from the secondary beams 49Fe/49V, respectively. The analogue properties of the reactions were used to help establish the new level scheme of 48Fe. The inclusive and exclusive cross sections were determined for the populated states. Large differences between the cross sections for the two mirrored reactions were observed and have been interpreted in terms of different degrees of binding of the mirror nuclei and in the context of the recent observations of suppression of spectroscopic strength as a function of nuclear binding, for knockout reactions on light solid targets. Mirror energy differences (MED) have been determined between the analogue T = 2 states and compared with the shell model predictions. MED for this mirror pair, due to their location in the shell, are especially sensitive to excitations out of the f 7 / 2 shell, and present a stringent test of the shell-model prescription. [ABSTRACT FROM AUTHOR]

Abstract: Excited states up to in the neutron-rich nucleus 58Cr have been identified by using a new experimental setup composed of the large acceptance magnetic spectrometer PRISMA and the highly efficient γ-detector array CLARA. Interestingly, the excitation energy sequence of the ground-state band follows the one expected by the dynamical symmetry for a nucleus at the critical point of the shape phase transition from a spherical vibrator () to a γ-soft rotor (). For the first time, in the same physical system, large scale shell-model calculations in the full fp shell are compared to the analytical model results and to the Interacting Boson Model. The theoretical results are in excellent agreement with the present data. [Copyright &y& Elsevier]

The γ-decay properties of 24Mg excited states are investigated in the inverse reaction 24Mg+12C at Elab(24Mg) = 130 MeV. At this energy the direct inelastic scattering populates a 24Mg&ast; energy region where 12C+12C breakup resonances can occur. Very exclusive data were collected with the Binary Reaction Spectrometer (BRS) in coincidence with EUROBALL installed at the VIVITRON Tandem facility of the IReS at Strasbourg. The experimental detection system is described and preliminary results of binary reaction coincidence data are presented. [Copyright &y& Elsevier]

The γ-ras from the decay of the GDR in the compound nucleus reaction 18O+28Si at bombarding enery of 105 MeV have been measured in an experiment using a setup consisting of the combined EUROBALL IV, HECTOR and EUCLIDES arrays. The shape of the rotating compound nucleus, 46Ti, is expected to undergo the Jacobi transition around spin 28 h̵. A comparison of the GDR lineshape data with the predictions of the thermal shape fluctuation model, based on the most recent rotating liquid drop LSD calculations, shows evidence for such Jacobi shape transition. In addition to the previously found broad structure in the GDR lineshape region at 18–25 MeV caused by large deformations, the presence of a low energy component (around 10 MeV), due to the Coriolis splitting in prolate, well deformed shape has been identified for the first time. [Copyright &y& Elsevier]

The spectroscopic quadrupole moment of the Iπ=Kπ=14+, T1/2=41 ns isomer in 176W has been measured by observing the time-dependent quadrupole interaction pattern of the decay radiation from the isomer implanted in the polycrystalline metallic Tl host. The result &z.sfnc;Qs&z.sfnc;=5.99(+0.66−0.82) eb corresponds to an intrinsic quadrupole moment Q0=7.37(+0.81−1.01) eb, similar to the ground-state band quadrupole moment. The value gR=0.269(34) has been deduced for the rotational g factor of the 14+ isomer on the basis of the measured static moments and branching ratios in the associated band. [Copyright &y& Elsevier]

High-efficiency arrays for γ spectroscopy, now available in several Laboratories, make possible the measurement of very weak cross-over transitions of high potential interest. A limit to the measurement possibilities comes, however, from the simultaneous detection of two γ-rays of a stop-over cascade (or “sum-up”), which cannot be distinguished from the true detection of the cross-over transition. We propose a new method to measure (and correct for) the sum-up effect, which can be used with symmetric γ detector arrays (like GASP and GAMMASPHERE), and discuss the possible techniques for identifying and estimating quantitatively the contribution of random pile-up, which can be sizeable at high counting rate. These ideas have been experimented at GASP in a dedicated measurement with a radioactive source of 52Mn. The results of this measurement are presented and discussed. Moreover, as a significant example, the method is applied to deduce the intensity of the E3 cross-over transition from the lowest 3− state of 148Gd. [Copyright &y& Elsevier]

Abstract: The differential Recoil Distance Doppler Shift (RDDS) method after multinucleon transfer (MNT) reactions to measure lifetimes of excited states in neutron-rich nuclei requires the use of a thick energy degrader for the recoiling ejectiles that are then detected in a spectrometer. This type of measurements greatly benefits from the use of the new generation segmented γ-ray detectors, such as the AGATA demonstrator which offers unprecedented energy and angular resolutions. In order to make an optimized choice of the material and the thickness of the degrader for lifetime measurements using the RDDS method after MNT, an experiment has been performed with the AGATA demonstrator. Counting rate measurements for different degraders are presented. [Copyright &y& Elsevier]