abstract

We present a theoretical interpretation of the cross sections to produce elements with atomic numbers \(Z = 102\)–118, in bombardments of a \(^{208}\)Pb target with projectiles ranging from \(^{48}\)Ca to \(^{86}\)Kr. The formation cross section is taken to be the product of three factors: the cross section for the projectile and target to stick, the probability for the resulting composite nucleus to reach the compound nucleus configuration by diffusion, and the probability for the latter to survive fission and to emit only one neutron. The first and third factors are treated according to more or less conventional formulae, whilst the middle one is based on the statistical (Brownian-like) diffusion of probability over a barrier in the form of an inverted parabola. The early dynamics of the neck growth is replaced by an assumption of a rapid injection into a macroscopically calculated asymmetric fission valley, after which the diffusion process begins. The measured cross sections can be reproduced fairly well by introducing an assumption about the separation between the surfaces of the approaching nuclei at which injection takes place. The optimum bombarding energies corresponding to the peaks of the excitation functions can be predicted by an elementary ‘optimum energy rule’, and the narrow widths of the measured excitation functions are readily accounted for.

abstract

Masses and \(\alpha \)-decay energies are calculated for very heavy nuclei with proton number \(Z=102\)–109. A macroscopic–microscopic approach is used. Much attention is also given to experimental values of these two quantities, deduced from energies of \(\alpha \) particles observed in \(\alpha \)-decay chains and from masses of finite nuclei in these chains. A comparison between calculated and experimental values is discussed. Other properties of the nuclei, such as deformations, shell-correction energies and deformation energies, are also studied.

abstract

Using the statistical model, we analyse the survival probabilities of excited heavy and superheavy nuclei. The calculated production cross sections of heavy neutron-deficient isotopes are in a good agreement with the experimental data for different de-excitation channels, especially near the maxima of excitation functions. The dependence of obtained values for superheavy nuclei produced in cold fusion reactions on different theoretical predictions of nuclear properties are discussed.

abstract

A theoretical model is presented for fusion mechanisms in massive systems, where the fusion process is divided into two steps; an approaching phase up to the contact of two incident ions and shape evolutions from the amalgamated configuration to the spherical shape. Results of the first step provide initial values for the second step. A qualitative explanation and a simple expression of the extra-push energy are obtained with an inverted parabola approximating the conditional saddle. Results obtained with more realistic two-dimensional model for shape evolutions are compared very well with the available data for \(^{48}\)Ca + actinide target systems. Remarks are given for synthesis of the superheavy elements.

abstract

The spectrum of prompt conversion electrons emitted by excited \(^{254}\)No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keV and comprises high multiplicity electron cascades, probably originating from \(M1\) transitions within rotational bands built on high \(K\) states. Evidence for the existence of isomeric states in \(^{254}\)No is presented.

abstract

The HD states were excited in the \(^{232}\)Th(\(n,f\)) reaction. By studying the mass and TKE distributions in the \(^{232}\)Th(\(n,f\)) reaction, some effect of the HD states was observed in the case of cold fission. The obtained data can be understood by assuming a predicted heavy clusterization.

abstract

The problem of symmetries within the redundant-variable method is revisited. Using physical conditions similar to those suggested by Bohr and Mottelson an appropriate symmetry subspace of the full space of the redundant-variable Hamiltonian has been constructed. Such a construction is a prerequisite condition for entering into any realistic calculation scheme.

abstract

Considering fission dynamics at low energy, shell and pairing effects can play a crucial role giving rise in particular to multimodal fission. To follow the evolution of the compound nucleus along its path to fission we solve a 2-dimensional Langevin equation taking explicitly particle evaporation into account. The fragment mass distribution and neutron pre-scission multiplicity obtained in a fusion-fission experiment performed in parallel are compared to the predictions leading to an improved theoretical description.

abstract

Heights of (static) spontaneous-fission barriers of heaviest nuclei are calculated within a macroscopic–microscopic approach. Even–even, odd-\(A\) and odd–odd nuclei with proton number \(Z\)=96–120 are considered.

abstract

Properties of states of the alternating parity bands, as well as super- and hyper-deformed states are analyzed within a cluster model.

abstract

Neutron separation energy, calculated within a macroscopic-microscopic approach, is presented for about 300 very heavy nuclei with proton number \(Z=102\)–120. Systematics of this energy, treated as a function of neutron number \(N\), is illustrated.

abstract

The Dubna Gas-filled Recoil Separator, operated at the U400 cyclotron at the Flerov Laboratory of Nuclear Reactions, is one of the most efficient existing separator systems used to separate heavy products of the complete fusion nuclear reactions. The system of detecting the compound nuclei \(\alpha -\)decay sequences and spontaneous fission events, data processing, readout and accumulation is described. The present system was successfully applied in our experiments aimed at the synthesis of superheavy elements with \(Z=116\) and \(Z=114\).

abstract

A review of some of the progress made in the study of nuclei at finite temperature and rotational frequency with the giant dipole resonance is here presented. The focus is the study of the low temperature region in connection with two different problems. The first is that of the shape and damping mechanisms of the GDR as deduced from radiative fusion among heavy ion symmetric reactions. The second is the effect of the GDR decay in the population of the superdeformed structures. Some perspectives for future works with radioactive beams will be also discussed.

abstract

Recent mean field calculations with effective interactions are discussed, and the relevance of corrections on top of these calculations, associated with the particle-vibration coupling, is emphasized.

abstract

We present a mean field quantum calculation of the superfluidity in the inner crust of neutron stars, taking into account the inhomogeneous character of the system, in which a lattice of neutron-rich nuclei coexists with a gas of unbound neutrons. We compare the resulting thermal properties of the star with those obtained neglecting the nuclear impurities.

abstract

We report on the experimental results (past and present) concerning the decay from superdeformed states in the mass 190 region and on the two extreme theoretical approaches used to model the process. These two approaches can be combined into one using a chaoticity parameter. The possibilities of studying order-to-chaos properties of normally deformed states are discussed and illustrated by the analysis of the primary decay-out strength distribution in \(^{194}\)Hg.

abstract

The presently most wanted information on neutrino properties concerns their mass values and their transformation properties under charge conjugation. The recent oscillation experiments prove that at least one of the three neutrino species has a non-vanishing rest mass and that the lepton flavour is not conserved. These findings have to be supplemented by data from phenomena of different kind in order to deduce the information needed. The most promising method proposed thus far to determine Majorana neutrino mass and thus to answer the two leading questions is to observe the neutrino-less double beta decay and to measure its rate. The physics of this process is discussed and the on-going and planned experimental search is reviewed. This search concentrates on the \(0{^+} \rightarrow 0{^+}\) ground-to-ground state decay of \({\beta ^-} {\beta ^-}\) emitters using calorimetric or \({\beta ^-} - {\beta ^-}\) coincidence tracking techniques. The \({\beta ^+} {\beta ^+}\) or \({\beta ^+}EC\) decays are usually considered as less favourable because of longer half-lives, even though they offer some advantages in combating the background. The recent proposition of measuring the monoenergetic photon spectra accompanying the radiative neutrino-less double electron capture decay is discussed. The experimental advantages of this technique may off-set the generally longer life-times expected.

abstract

The problem of the conservation of the \(K\)-quantum number at high spin and high-excitation energy is investigated making use of a large statistics data set on the \(^{163}\)Er nucleus, obtained with the EUROBALL array. In particular, the ridge structure, observed in \(\gamma \)–\(\gamma \) coincidence matrices and typical of the rotational motion, is analysed for high and low values of the \(K\) quantum number. The experimental results are compared with cranked shell model calculations taking into account the residual interaction and for which the \(K\)-quantum number of the band can be traced also in the warm rotation.

abstract

We investigate the use of an operatorial basis in a self-consistent theory of large amplitude collective motion. For the pairing plus quadrupole model we show that a small set of basis operators is sufficient to approximate the exact solution of the problem accurately.

abstract

The electromagnetic decay properties of high spin states in \(^{52}\)Mn have been carried out with the GASP and EUROBALL arrays combined with the charged-particle detector ISIS and the Neutron-Wall. From the coincidence measurements in these experiments new high spin states were placed in the \(^{52}\)Mn level scheme. In a recent experiment performed at the on-line mass separator at GSI, the decay properties of the 12\(^+\) yrast trap in \(^{52}\)Fe have been investigated. Two E4 gamma branches to the 8\(^+\) states in \(^{52}\)Fe have been observed for the first time and the beta decay into high spin states in \(^{52}\)Mn has been revisited.

abstract

Above angular momentum \(10^+\), we found two positive-parity sequences, connected by energetically staggered \(\Delta I = 1\) M1 transitions. The total Routhian surface calculations predict a strong triaxial deformation for them. To our knowledge, this is the first observation of staggered M1 transitions in a deformed four-quasiparticle \(\pi (g_{9/2}^2) \nu (g_{9/2}^2)\) regime.

abstract

The low–lying collective excitations of \(^{98}\)Mo were investigated within microscopic collective Bohr Hamiltonian modified by the coupling with pairing vibrations. Some discrepancies with experimental data concerning the \(0^+_2\) excitation and the interpretation of this state in terms of isoscalar (\(T=0\)) and isovector (\(T=1\)) bosons suggest that the collective Hamiltonian should be completed with proton–neutron pairing vibrations.

abstract

A realistic nuclear mean-field Hamiltonian with pairing has been diagonalized using Fock space representation that allows for nearly exact treatment of the problem. Calculations were performed for all the even–even nuclei with \(Z \in (20, 100)\), whose pairing gaps were possible to extract out of the experimental masses. The optimal values of the pairing strength constants for the protons and neutrons have been found.

abstract

A partial decay scheme for \(^{128}\)Xe is presented. The \(K^{\pi }=8^-\) state is isomeric with a half-life of 73(5) ns. Theoretical calculations have been performed using the configuration constrained blocking method based on a non-axial Woods–Saxon potential. Large \(\gamma \)-deformation and \(\gamma \)-softness have been predicted for the ground state. The strong shape-driving effect of the \(K^{\pi }=8^-\) state results in a much smaller value of \(\gamma \) for this configuration. This may partly explain the isomerism, despite the \(\gamma \)-softness. Measured hindrance factors are discussed in the context of the \(\gamma \)-softness of this nucleus.

abstract

We report here on a shell-model study of nuclei close to doubly magic \(^{132}\)Sn and \(^{100}\)Sn focusing attention on particle–hole multiplets. In our study we make use of realistic effective interactions derived from the CD-Bonn nucleon–nucleon potential. We present results for the four nuclei \(^{132}\)Sb, \(^{130}\)Sb, \(^{102}\)In and \(^{98}\)Ag. Comparison shows that the calculated results are in very good agreement with the experimental data available for these nuclei far from stability. This supports confidence in the predictions of our calculations which may stimulate, and be helpful to, future experiments.

abstract

The origin of new shell structure observed in neutron-rich light nuclei and implications for medium-heavy nuclei are discussed in terms of the monopole part of the in-medium \(NN\) interaction. The evolution of the harmonic oscillator (HO) closed shells \(N=8,20,40\) via shell gap quenching towards \(N_m-2N\), with \(N\) numbering HO quanta, is compared to recent experimental data. The locality of the monopole driven shell change and the fading of its shell quenching power beyond \(N=50\) is discussed.

abstract

In the present work triple, prompt \(\gamma \)-ray coincidence data following the spontaneous fission of \(^{248}\)Cm have been used to search for excited bands in neutron-rich nuclei based upon two-quasiparticle intrinsic structures. Such bands have been found in several even–even nuclei from \(^{96}\)Sr to \(^{112}\)Pd. Careful analysis of double-gated spectra has been performed in order to determine branching ratios within the bands. These branching ratios are then used to establish the magnetic properties of the intrinsic structure, permitting, in many cases, the determination of which Nilsson orbits (and whether they are neutron or proton states) are contributing to the excitation. The results of the investigation are presented, and the single-particle states involved in the two-quasiparticle excitations in some of the nuclei studied are identified. The lowest-lying two-quasiparticle states will be at an excitation energy of approximately 2\({\mit \Delta }\) above the even–even ground state. If these lowest-lying bands are systematically populated, then it would allow us to determine the single-particle orbits at the Fermi surface as the nuclear mass number and deformation varies. One interesting feature that arises from the present study is that the population mechanism in fission plays an important role in deciding what two-quasiparticle states are actually observed.

abstract

The shell model has been particularly successful in describing the structure of states near the doubly magic \(^{208}\)Pb core. In particular semi-empirical calculations are able to reproduce the yrast states in the three valence proton nucleus, \(^{211}\)At to a high degree of accuracy. Recent spectroscopic measurements using a variety of novel reaction mechanisms have provided information on the related \(A = 211\) nuclei \(^{211}\)At, \(^{211}\)Po \(^{211}\)Bi and \(^{211}\)Pb allowing a comparison between the data and the results of semi-empirical calculations. While good agreement is observed for the lower spin yrast states, the calculations predict the presence of isomeric states not yet completely characterized in the current experiments.

abstract

A simple three-parameter supersymmetric mass formula has been applied to binding energy calculations of nuclei in the \(s\)–\(d\) shell grouped into supermultiplets. The earlier suggestion of instability of \(^{26}\)O has been confirmed and binding energies of other exotic nuclei have been predicted.

abstract

The \(^{180}\)Re nucleus has been studied at high angular momentum using the \(^{174}\)Yb(\(^{11}\)B,\(5n\)) reaction at the Australian National University, with the CAESAR array for \(\gamma \)-ray detection and the Super-E solenoid for electron-conversion measurements. A \(\tau =13\pm 1~\mu \)s, 6-quasiparticle isomer and two intrinsic states and their associated bands have been established. The validity of the \(K\) quantum number is discussed.

abstract

The \(^{98}\textrm {Mo}\)(\(^{16}\textrm {O}, xn\)) reaction has been used to study the level structure of the semi-magic nuclei \(^{110}_{50}\)Sn, \(^{111}_{50}\)Sn and \(^{112}_{50}\)Sn. The OSIRIS-II array equipped with 10 HPGe detectors with anticompton shields was used in conjunction with an 48-element BGO multiplicity filter. The experiments performed with projectile energy \(E_{^{{16}}{\rm O}}=60\)–80 MeV brought results on relative excitation functions, \(\gamma \)-ray angular distributions, as well as on \(\gamma \)–\(\gamma \) and \(\gamma -t_{\rm RF}\) coincidences. The measurements include also \(\gamma \)-ray multiplicity and total energy data as well as the investigations of radioactive decays. The selected results on the properties of excited states in the studied nuclei are reported. In particular, the evidence for a neutron-core coupling in \(^{111}\)Sn, and the extension of the intruder and negative parity bands in \(^{110}\)Sn and \(^{112}\)Sn nuclei are presented.

abstract

Selected experimental results retrieved from \(^{98}{\rm Mo}(^{16}{\rm O}, xnyp)\) reaction are discussed and compared with the up-to-day known data. The collective configurations in selected \(Z=48\)–50, \(N=55\)–66 nuclei are presented in terms of Cranked Shell Model (CSM) and rigid rotor description. The special interest was put on: (1) Systematical behaviour of intruder bands especially for low spin levels, (2) The collective, strongly coupled bands, where the band members are connected by \(\Delta I=1\) transitions, (3) Smooth band termination in the \(A=104\)–120 mass region.

abstract

A new 7 \(\mu \)s isomer in the drip line nucleus \(^{140}\)Dy was selected from the products of the \(^{54}\)Fe (315 MeV) + \(^{92}\)Mo reaction by a recoil mass spectrometer and studied with recoil-delayed \(\gamma \)–\(\gamma \) coincidences. Five cascading \(\gamma \) transitions were interpreted as the decay of an \(I^\pi =8^-\) \(\{\nu 9/2^- [514] \otimes \nu 7/2^+ [404]\}\) \(K\) isomer via the ground state band.

abstract

The previously known level scheme of \(^{141}\)Eu nucleus was revised and substantially extended. Three dipole cascades, characterized by large B(M1)/B(E2) ratios, have been found. Spin and parity assignments were based on the angular distribution ratios and linear polarizations of \(\gamma \)-rays. The experimental results have been compared with the calculations of Tilted Axis Cranking (TAC) model.

abstract

Coulomb breakup of high-energy secondary beams of unstable nuclei serves in nuclear structure investigations of neutron-rich isotopes. A summary of the respective research activities at GSI is presented, covering isotopes from helium to oxygen. The breakup is mediated through dipole excitations into the continuum. Non-resonant excitations into the continuum near the dissociation threshold deliver information on the single-particle ground-state structure. Resonant excitation into the giant resonance domain is also observed. In addition, a brief outlook on future activities at GSI is given.

abstract

This talk is a brief overview of strongly interacting matter phase transition studies. To begin with, I will discuss the phase transition of nuclear matter investigated in intermediate energy domain of heavy ion collisions. Then I will jump to the relativistic energies to review the fixed target experimental signatures of the quark–gluon plasma phase transition. The recent experiments at the ultrarelativistic collider energies will also be introduced. Finally, I will shortly mention a new project dedicated to investigate the novel states of dense baryonic matter.

abstract

Highly excited and rapidly rotating compound nuclei (CN) produced in fusion-evaporation (FE) reactions can be well investigated by using charged particle spectroscopy. In such hot nuclei, with excitation energies as high as \(E^{*}_{\rm CN} = 80\) MeV, the spectral shapes of \(\alpha \) particles provide information on the nuclear deformation. We report here on in-plane light charged particle (LCP) — heavy-ion (HI) coincident measurements for the \(^{16}{\rm O} + ^{28}\)Si reaction. The experiment was carried out at three bombarding energies, \(E_{\rm lab}(^{16}{\rm O}) = 76\), 96 and 112 MeV with the multidetector array ICARE at the VIVITRON Tandem facility. The Monte Carlo version of the statistical-model code CASCADE, which describes the FE process, has been used to characterize the \(^{44}\)Ti CN. A unique set of deformability parameters reproduces well the experimental \(\alpha \) spectra to the three bombarding energies. The discrepancies observed for the proton spectra are still to be explained.

abstract

Many open questions regarding the study of reaction mechanisms with heavy ions have still to be solved, even in the energetic range between 5 and 20 MeV/\(u\), which is covered by the accelerating system Tandem XTU–Linac ALPI of the Laboratori Nazionali of Legnaro. Using complex apparatuses like GARFIELD, coupled with different ancillary detectors, it is possible to perform exclusive measurements, which should be capable of giving new important information, in order to better understand both nuclear structure problems, like for example the study of the mechanisms underlying the Giant Dipole Resonance Damping, and reaction mechanisms phenomena, like the characterization of those mechanisms which are responsible for the many-fragment emission. Preliminary results and future plans to be performed with the GARFIELD facility have been described.

abstract

In experiments performed at the GSI Fragment Separator and at the GANIL SISSI-LISE3 facility the decay of \(^{45}\)Fe has been investigated. Implantation events of \(^{45}\)Fe ions, stopped in silicon telescopes, were correlated with radioactive decay events. The decay energy spectra exhibit a peak of an average energy of (\(1.14 \pm 0.05\)) MeV. This observation, together with the non-observation of coincident \(\gamma \) or \(\beta \) events, represent clear evidence for the two-proton ground state decay of \(^{45}\)Fe. The average half-life of \(^{45}\)Fe, deduced from both experiments, is \(T_{1/2} = 3.8 ^{+2.0}_{-0.8}\) ms.

abstract

Marian Smoluchowski is considered to be the founder of the physics of stochastic processes. In his studies of the Brownian motion he showed how the underlying thermal motion of the optically invisible molecules can be inferred from the observation of the chaotic motion of suspended colloidal particles discernible by the microscope. Smoluchowski was first to introduce randomness into physical equations. We show how the basic concepts and equations derived by Smoluchowski can be used to study the various forms of nucleonic matter excited in collisions of heavy ions, the liquid-to-gas phase transition in nuclei, multifragmentation phenomena and the possible transition to the quark–gluon plasma, the ultimate state of hadronic matter. The partonic structure of baryons can be studied from the energy and angular distributions as well as correlations of emitted hadrons even if Nature does not allow us to see free quarks and gluons. The various achievements of Smoluchowski’s work, like the diffusion equation, fluctuation analysis, critical phenomena close to phase transitions, and foundations of the coalescence model as applied to contemporary problems are discussed, and their universality is stressed.

abstract

Studies of \(^{15}\)C and \(^{11}\)Be nuclei has been dealt with the (\(^{7}\)Li,\(^{7}\)Be) charge exchange reaction at 57 MeV. The energy spectrum at 10\(^{\circ }\) of \(^{15}\)C nucleus is presented and discussed in comparison with the \(^{11}\)Be one. An explanation of the \(^{15}\)C energy spectrum is proposed in relation to Dynamical Core Polarization calculations for the single particle strength function.

abstract

Elastic cross sections for the scattering of \(^{6}\)He projectiles by \(^{208}\)Pb at 27 MeV have been studied. The data have been analyzed within the framework of the Optical Model using Saxon–Woods phenomenological form factors for both the real and imaginary parts of the nuclear potential. The elastic scattering data suggests the presence of a long range absorption mechanisms which might be related to the halo structure of \(^6\)He.

abstract

Projectile fragmentation of a 750 MeV/nucleon \(^{238}\)U beam was used to populate neutron-deficient nuclei around \(A\sim 190\). Isomeric states in Hg, Tl, Pb, Bi, and Po isotopes were identified and their lifetimes determined, with the ultimate aim of measuring their isomeric ratios to provide information on the spin population in such reactions.

abstract

Statistical emission of high-energy photons in heavy-ion reactions \(^{20}\)Ne+\(^{12}\)C \(\to ^{32}\)S at 5.2 MeV/\(u\) and \(^{19}\)F+\(^{12}\)C \(\to ^{31}\)P at 4.4 MeV/\(u\) has been studied and the Giant Dipole Resonance strength functions in \(^{32}\)S and \(^{31}\)P at excitation energy of 58 and 55 MeV have been extracted. Possible isospin and deformation splitting of the GDR are discussed. The derived isospin mixing coefficient for \(^{32}\)S states at 58 MeV excitation is presented.

abstract

The present status of glueballs search is shortly reviewed, with special emphasis on search in proton-antiproton annihilation. The lattice QCD predictions for glueball mass spectrum are presented. We discuss the main requirements for the detector for glueball searches with the planned High Energy Storage Ring (HESR) at GSI Darmstadt. The parameters of the HESR are also given.

abstract

The \(\alpha \) particle emission process through the multidimensional barrier potential has been considered. The deformed nucleus-\(\alpha \) particle interaction energy including proximity approximation in the nuclear potential and Coulomb terms have been proposed. The alpha decay of very heavy arbitrarily deformed nuclear systems have been studied within the above potential. The curvature effects have been also investigated.

abstract

Experimental data for elastic and inelastic scattering of \(^{11}\)B ions by \(^{12}\)C nuclei measured recently at the Warsaw Cyclotron were analyzed by means of the coupled-reaction-channel method. Rotational model for the low-lying states in \(^{11}\)B and \(^{12}\)C was assumed. The deformation lengths for the \(^{11}\)B and \(^{12}\)C ground states as well as for the \(^{11}\)B \(3/2^-\) excited state (\(E_x = 5.02\) MeV) were extracted from the analysis. Contrary to the theoretical predictions the deformation length of the \(^{11}\)B \(3/2^-\) excited state was found to be large, close to that of the ground state.

abstract

The structure of nuclei situated far from the line of \(\beta \) stability is presently one of the major thrusts in nuclear physics. The phenomenon of proton emission offers a unique opportunity to study nuclei beyond the proton dripline. Within the last decade proton-decay studies have been transformed from a curiosity into a powerful spectroscopic tool. Experimental effort has resulted in the observation of deformed proton emitters, the discovery of proton-decay fine structure and the observation of excited states in several proton emitters. Thank to continuous progress in experimental techniques the body of data on proton emission is steadily increasing. Several theoretical models have been developed to quantitatively reproduce proton-decay widths. The role of Coriolis mixing, non-axial degrees of freedom, proton-neutron interaction, coupling to core vibrations are some of the aspects currently under investigation. This paper discusses recent progress on the understanding of proton decay. It will be illustrated by experimental results obtained at the Argonne National Laboratory within the last 2 years.

abstract

The coupling of big Ge-arrays like EUROBALL or GASP with ancillary detectors for the study of the structure properties of very exotic nuclei, far from the stability valley, has given outstanding results in the last years. A large fraction of the experiments performed with both arrays has been devoted to study both proton-rich and neutron-rich nuclei populated using stable beams provided by the LNL Legnaro and IReS Strasbourg accelerators. Nuclei lying close to the \(N=Z\) line are of particular interest being a laboratory where collective excitations as well as fundamental properties of the nuclear force can be tested, like isospin symmetry and isospin breaking terms, proton neutron pairing, dripline effects and coherent neutron and proton contributions to the nuclear excitations. Some of this properties are more evident (degree of isospin mixing) or can be only observed (collective effects) in heavy \(N=Z\) nuclei. In this contribution we present the experimental results obtained by our collaboration along and in the vicinity of \(N=Z\) line.

abstract

The \(\beta \) decay of the proton-rich nuclei \(^{94}\)Ag and \(^{100}\)In was investigated at the GSI on-line mass separator by using different arrays of Ge and Si detectors, as well as a total absorption spectrometer (TAS). The preliminary analysis of the \(\beta \gamma \gamma \) coincidences in case of \(^{94}\)Ag confirms the existence of all \(\gamma \) rays observed in a previous measurement and forms the basis for an improved decay scheme. In the case of \(^{100}\)In, the population of states up to the 8\(^+\) yrast state in \(^{100}\)Cd has been identified from \(\beta \gamma \gamma \) coincidences. The experimental \(\beta \) feeding measured in the TAS is compared to predictions of large-scale shell-model calculations, which favour a spin and parity of 6\(^+\) for the \(^{100}\)In ground state.

abstract

We report on the first Coulomb excitation experiments of a radioactive beam provided by the Spiral facility at GANIL (France) to study the shape of the unstable isotope \(^{76}\)Kr.

abstract

Lifetimes of excited states with spin \(I^{\pi }=23/2^{-}-39/2^-\) belonging to the \(\pi h_{11/2}\) band in \(^{131}\)La have been measured using the DSA method. The \(^{131}\)La nuclei were produced in the \(^{122}\)Sn(\(^{14}\)N,\(5n)^{131}\)La reaction at \(E(^{14}\)N\()=70\) MeV. Experimental data for the \(h_{11/2}\) band in \(^{131}\)La have been compared with the CQPC and TRS model calculations. The additional experiment has been done to determine the stopping power parameters.

abstract

A Monte Carlo simulation of the EUROBALL Neutron Wall has been performed using GEANT4 to study the problem of scattering of neutrons. It has proven possible to identify a large fraction of the scattered neutrons. This can be used to enhance the two neutron compared to the one neutron reaction channel in events where two neutrons have been detected by a factor as large as \(35\), to the cost of loosing \(80\%\) of intensity in the two neutron reaction channel. For events with three neutrons detected an enhancement of three neutron compared to two neutron reaction channels of \(20\) is possible to the cost of loosing \(92\%\) of the three neutron intensity. The results of the simulations have been compared to experimental data.

abstract

Using effective nucleon-nucleon interactions of the Skyrme type and the semi-classical extended Thomas-Fermi approach we describe heavy-ion fusion barriers in the sudden approximation. We review in particular a large number of fusion reactions leading to the superheavy element \(Z \!=\! 114\).

abstract

We present an attempt to describe collective quadrupole excitations in medium heavy transitional nuclei starting from HF-BCS approach with Skyrme SIII forces. The collective dynamics is treated through the Bohr Hamiltonian with mass parameters and moments of inertia calculated microscopically in the cranking approximation. Theoretical energy levels and \(B(E2)\) transition probabilities for \(^{102}\)Zr, \(^{104}\)Mo, \(^{110}\)Ru, \(^{110}\)Pd, \(^{124}\)Xe and \(^{126}\)Ba nuclei are compared with experiment.

abstract

In recent attempts to search for exotic shapes, hyperdeformation (HD), and Jacobi transitions in Hf, Ba, Xe, Sn and Nd nuclei, ridge structures presumably originating from nuclei of very elongated shapes have been observed in \(^{126}\)Ba, with Gammasphere (GS) and in \(^{126}\)Xe, with Euroball-IV (EB-IV). After the promising results from GS, a second experiment in \(^{126}\)Ba followed at EB-IV, taking advantage of the use of the BGO Inner Ball (IB) for selecting the highest spins. The decay of the Giant Dipole Resonances (GDR) is also studied, and the analysis in progress. The Quasi-continuum transitions in the Jacobi region, show a significant decrease in energy for both \(^{126}\)Ba and \(^{126}\)Xe, compared to the Thomas–Fermi- and the LSD model predictions. Similar effects were recently found for other nuclei by Ward et al.

abstract

A novel \(4\pi \) \(\gamma \)-detector array designed as a closed shell of Ge crystals is currently under development. It will consist of 180 large Ge crystals. For the first time pulse shape analysis and \(\gamma \)-ray tracking will be employed to distinguish \(\gamma \)-rays scattering inside the shell and to determine the point of impact. A full energy peak efficiency of 50% at multiplicity \(M=1\) and up to 24% at \(M=30\) are expected, resulting in a sensitivity increase of up to three orders of magnitude for subtle nuclear structure investigations.

abstract

We present possible manifestations of octahedral and tetrahedral symmetries in nuclei. These symmetries are associated with the O\(_h^{\rm D}\) and T\(_d^{\rm D}\) double point groups. Both of them have very characteristic finger-prints in terms of the nucleonic level properties — unique in the Fermionic universe. The tetrahedral symmetry leads to the four-fold degeneracies in the nucleonic spectra; it does not preserve the parity. The octahedral symmetry leads to the four-fold degeneracies in the nucleonic spectra as well but it does preserve the parity. Microscopic predictions have been obtained using mean-field theory based on the relativistic equations and confirmed by using ‘traditional’ Schrödinger equation formalism. Calculations are performed in multidimensional deformation spaces using newly designed algorithms. We discuss some experimental fingerprints of the hypothetical new symmetries and possibilities of their verification through experiments.