abstract

Natural radioactivity was discovered by Henri Becquerel in February, 1896, but for over two years it remained on the periphery of interest of physicists. It was the research by Maria Skłodowska-Curie and then also by her husband Pierre in 1898 that began a new era in physics.

abstract

Hundred years after the birth of nuclear physics almost 3000 bound nuclides are known. Most of them have been produced in nuclear laboratories. With help of new experimental tools, like beams of relativistic heavy ions and projectile fragment separators, still new territories on the chart of nuclei are being conquered. A few examples of experiments which have recently shifted the limits of known nuclei will be presented.

abstract

We address the question concerning the maximum density, \(\rho ^{\cal N}_{\rm max}\), at which nuclei (and more generally — nuclear structures) can exist in neutron star interiors. An absolute upper bound to \(\rho ^{\cal N}_{\rm max}\) is obtained using the bulk approximation, in which surface and Coulomb effects are neglected. A very good approximation to \(\rho ^{\cal N}_{\rm max}\) is given by the threshold for the instability of a uniform \(npe\) plasma with respect to density modulations; this threshold is calculated using the Extended Thomas–Fermi approximation for the Skyrme energy functionals. For recent SLy Skyrme forces, which are particularly suitable for the description of very neutron rich nucleon systems, one gets \(\rho ^{\cal N}_{\rm max}=0.08~{\rm fm^{-3}}\); at this density protons constitute only 4% of nucleons.

abstract

New results obtained in spectroscopic studies of three-valence -particle nuclei \(^{211}\)Po and \(^{135}\)Te are presented. Yrast states above the \(\alpha \)-decaying isomer in \(^{211}\)Po have been located in the \(\gamma \)-ray studies of deep-inelastic products of 450 MeV \(^{76}\)Ge + \(^{208}\)Pb collision. Prompt \(\gamma \)-ray cascades in \(^{135}\)Te fission product nucleus have been measured at GASP using a \(^{252}\)Cf source. Coincidences across the 0.5 \(\mu \)s 19/2\(^{-}\) isomeric state in \(^{135}\)Te displayed the \(\gamma \)-rays feeding the isomer. Similarities between the yrast structures in \(^{211}\)Po and \(^{135}\)Te nuclei are discussed.

abstract

The recent developments at the IGISOL-facility in Jyväskylä are reviewed. The spectroscopy of fission products has revealed a new set of beta-delayed neutron emitters and resulted in an identification of new isotopes in the \(A=110\) region. The new results on level structures of even-even refractory fission products imply the population of the two-quasiparticle structures. The spectroscopy of light fission products has lead to the observation of superasymmetric fission. The implementation of the heavy-ion ion guide has opened the possibility to apply the ion guide technique to medium and heavy neutron-deficient nuclei. Its performance in the vicinity of the \(N=Z\) line is summarized. The highlights of the research on the light proton-rich nuclei are given as well as the recent results of the collinear laser spectroscopy at IGISOL. The new project of mass-selective cooling and bunching of ion beams from the IGISOL-separator is presented.

abstract

By means of the HIGISOL technique, the \(A=125\) mass chain was studied via \(\beta ^+\)/EC decay of \(^{125}\)Ce and a new (\(350^{+60}_{-40}\))ms isomer was definitely assigned to \(^{125}\)La based on conversion electron measurements.

abstract

An extensive program to study the production, decay properties, and nuclear structure of very neutron-deficient polonium and radium nuclei is underway at the Department of Physics, University of Jyväskylä, Finland (JYFL). The main tools used in these studies are the gas-filled recoil separator RITU and various germanium gamma-ray arrays. In the course of these studies, among others the following new isotopes have been produced: \(^{204}\)Ra, \(^{203}\)Ra, and \(^{202}\)Ra. Isomeric alpha decaying states have been discovered in \(^{203}\)Ra and \(^{191}\)Po. Fine structure in the decay of \(^{192}\)Po to the oblate and prolate band heads in \(^{188}\)Pb has been observed. In-beam gamma-ray spectra have been, for the first time, measured for \(^{192}\)Po, \(^{206}\)Ra, \(^{208}\)Ra, and \(^{210}\)Ra. Development of collectivity in nuclei in the Po-Ra region and the systematics of reduced alpha widths will be discussed.

abstract

The \(\alpha \)-decay properties of the neutron-deficient \(^{191}\)Po and \(^{191}\)Bi nuclei have been investigated at the RITU gas-filled separator using the 5n and p4n evaporation channels of the \(^{36}\)Ar\(+^{160}\)Dy\(\to ^{196}\)Po\(^{*}\) reaction. In contrast to previous studies two \(\alpha \)-decaying isomeric states were observed in the decay of \(^{191}\)Po. Evidence was found for \(\alpha \)-decay to excited levels in the \(^{187}\)Pb daughter nucleus. The tentative interpretation of these levels could be a weak coupling of the odd neutron to an intruder \(2p\)–\(2h\) deformed 0\(^+\) state in the even-even core. The difference in the reduced \(\alpha \) widths of the \(\alpha \) transitions towards the ground state and excited state points to a deformed 13/2\(^+\) isomeric state in \(^{191}\)Po. Branching ratios of \(b_{\alpha }\)(\(^{187m}\)Pb)=12(2)\(\%\) and \(b_{\alpha }\)(\(^{187g}\)Pb)=7(2)\(\%\) have been experimentally measured. For \(^{191}\)Bi two new alpha-lines have been observed. A more precise half-life value of \(T_{1/2}=115\)(10)ms was determined for \(^{191m}\)Bi.

abstract

The fission probability has been measured in the \(^{239}\)Pu\((d,pf)^{240}\)Pu reaction as a function of the excitation energy. A new resonance group was found in the excitation energy region of 4.4-4.8 MeV and was interpreted as superdeformed rotational bands with an observed rotational parameters of \(\hbar ^2/2{\mit \Theta }\) = 3.2 keV corresponding to the superdeformed nuclear shape.

abstract

In-beam \(\gamma \)-ray and \(\gamma \)–\(\gamma \) coincidence measurements have been made for the very neutron deficient nucleus \(^{176}\)Hg using the recoil-decay tagging (RDT) technique. The irregular yrast sequence observed to \(I = 10\hbar \) indicates that the prolate intruder band, seen in heavier Hg isotopes near the neutron midshell, is crossing the nearly spherical ground-state band of \(^{176}\)Hg above \(I = 6\hbar \).

abstract

The lifetime of levels in the yrast band of \(^{119}\)I were measured by DSAM and RDM using the \(^{109}\)Ag(\(^{13}\)C,3n) reaction at \(E=54\) MeV. The detailed description of data analysis including the stopping power determination and estimation of side feeding time is given. A modified method of RDM data analysis — Recoil Distance Doppler Shape Attenuation (RDDSA) is used.

abstract

The current knowledge of octupole phenomena in radium isotopes is reviewed. The systematic behaviour of the low-lying structure of these heavy nuclei will be discussed, with emphasis on their energy levels and electromagnetic moments. Prospects for developing new probes of asymmetric charge and mass distributions will also be discussed.

abstract

The large gain in sensitivity provided by powerful new \(\gamma \)-ray detector arrays, such as Gammasphere, coupled with other advances in the field of heavy-ion induced Coulomb excitation, open exciting new research opportunities for exploiting Coulomb excitation to probe nuclear structure. Three recent examples are given that exploit this unprecedented sensitivity. The actinide nuclei \(^{248}\)Cm and \(^{240,242,244}\)Pu have been Coulomb excited using \(^{208}\)Pb ions at the barrier. The positive and negative-parity yrast bands have been extended to high spin, \(\le 34\hbar \), and the evolution of alignments probed. Heavy-ion induced Coulomb excitation of a \(^{162}\)Dy beam is providing significant new information on states to high spin in the ground, \(S\) and \(\gamma \) bands, as well as a double \(\gamma \)-phonon band. Collective octupole correlations are especially strong in \(^{208}\)Pb and \(^{96}\)Zr implying the possible existence of localized octupole double-phonon states in these nuclei. Heavy-ion Coulomb excitation has been used to locate octupole double-phonon strength in these nuclei; the results for \(^{208}\)Pb show large fragmentation of the octupole double-phonon strength whereas a major fraction of the strength may have been located for \(^{96}\)Zr.

abstract

Coulomb excitation has been proved as a powerful tool to study the electromagnetic structure of the nuclei. In particular this method is able to determine large sets of electric and magnetic multipole matrix elements, giving an insight into the overall structure of the nuclei in the low- energy and relatively low-spin excitation region. This application of multiple Coulomb excitation is exploited since almost two decades. In this contribution we would like to concentrate on a different usage of the Coulomb excitation technique — addressing specific physical problems by choosing the experimental conditions in a way that enhances the sensitivity to the effect under investigation. As an example the direct measurement of the E3 coupling between gamma-vibrational and pseudo-beta-vibrational bands in \(^{148}\)Nd is discussed. The results presented demonstrate how relatively simple measurement can be designed to investigate non-trivial phenomena.

abstract

The nucleus \(^{231}\)Pa was studied by Coulomb-excitation. New states were identified by particle-\(\gamma \gamma \) coincidences using the NORDBALL array in coincidence with two different particle detector systems. A regular band-structure is observed in the \(3/2[651]\) band for levels above \(9/2+\) fed by strong E1 transitions from the ground-state band.

abstract

The depopulation of \(^{180\rm {m}}\)Ta by Coulomb excitation was investigated. The recoiling tantalum ions from bombardments with \(^{36}\)S and with \(^{64}\)Ni were collected in catcher foils surrounding the beam. The out-of-beam identification of the 8h decay of \(^{180\rm {gs}}\)Ta in these foils leads to the existence of a mediating state at about 1.3 MeV excited from \(^{180\rm {m}}\)Ta by an E3 transition of the order of several Weisskopf units.

abstract

We review proposed production mechanisms of \(^{180}\)Ta during the nucleosynthesis process. In this nucleus, an electromagnetic coupling between the ground state and the \(9^-\) isomeric state may strongly affect the produced abundances. Possible theoretical electromagnetic paths between the ground state and the isomeric state are discussed in the framework of the two-quasiparticle-plus-phonon model and the standard axially-symmetric rotor model including Coriolis mixing.

abstract

We investigate the properties of the Giant Dipole Resonance (GDR) built on very exotic nuclear systems: (i) High temperature, at the limit of nuclear stability. We discuss first the problem of hot nuclei formation then we analyse the possibility of observation of a zero- to first sound transition for the dipole propagation. (ii) Shape and charge equilibration in fusion dynamics. We describe the features of direct GDR photon emissions from intermediate dinuclear systems with very exotic shapes or charge distributions formed in particular entrance channels (mass symmetry vs. charge symmetry). (iii) Isospin. We show the effect of large charge asymmetry on propagation of isovector modes. Mixing to isoscalar components and possible new instabilities are predicted, related to the structure of the symmetry term of effective interactions.

abstract

The \(\gamma \)-decay of the Giant Dipole Resonance, GDR, built on excited states of compound nuclei is discussed as a source of high-energy \(\gamma \)-ray emission in complete fusion reactions at projectile energies up to 5 MeV/u. Some results of the GDR studies are presented, also those measured at the Warsaw Cyclotron for the \(^{12}\)C\( + ^{58, 64}\)Ni reactions at 47.5 MeV by using the new multi-detector system JANOSIK. The mechanism of heavy-ion collisions and sources of high-energy \(\gamma \)-ray radiation occurring at projectile energies of 6–11 MeV/u are also described. At these energies, besides statistical GDR decay, another process involving bremsstrahlung radiation becomes important. It is shown that in mass-asymmetric reactions, such as \(^{12}\)C\( + ^{24, 26}\)Mg and \(^{12}\)C\( + ^{58, 64}\)Ni, the two types of \(\gamma \)-ray emission may be disentangled by the angular distribution measurement. The data when properly analyzed may give information on the GDR built on excited states as well as on the bremsstrahlung process.

abstract

Three topics concerning the \(\gamma \)-decay of the Giant Dipole Resonance in hot rotating nuclei from recent exclusive experiments with the HECTOR array are discussed. The first is the dependence of the GDR width in Sn nuclei as a function of angular momentum at constant temperature. The second is the search for \(\gamma \)-decay of the GDR build on superdeformed configurations in the \(^{143}\)Eu nucleus. The third is the study of reaction entrance channel effects in the decay of the compound \(^{170}\)W nucleus.

abstract

The damping of the collective vibrations in hot nuclei is studied within the semiclassical Vlasov–Landau kinetic theory. The extension of the method of independent sources of dissipation is used to allow for irreversible energy transfer by chaos weighted wall formula. The expressions for the intrinsic width of the giant multipole resonances are obtained. The interplay between the one-body and the two-body channels which contribute to the formation of the intrinsic width in nuclei is discussed.

abstract

Atomic spectroscopy measurements were carried out using the COMPLIS setup installed at the ISOLDE-BOOSTER facility. Hyperfine structure (HFS) spectra and isotope shift (IS) values were obtained for the neutron-deficient \(^{178-185}\)Pt and for \(^{184}\)Au\(^{g,m}\), providing deformation parameters \(\beta \), magnetic moments \(\mu \) and spectroscopic quadrupole moments (for \(I \geq \) 1) \(Q_{s}\) . In Pt isotopes, a deformation drop for \(A=178\) and an inverted odd-even staggering for the charge radius around the neutron mid-shell \(N=104\), have been observed very clearly. Furthermore, deformation changes \(\delta \beta \) between isomeric and ground states for \(^{183,185}\)Pt and \(^{184}\)Au have been put forward. Thus, the influence of the proton-neutron coupling on the \(\delta \beta \) value in \(^{184}\)Au relatively to that in its isotone \(^{183}\)Pt has been determined. Besides, the \(h_{9/2}\) proton state that is decoupled from the core in \(^{183,185}\)Au, becomes the 3/2 [532] state strongly coupled in \(^{184}\)Au. The spin and parity values \(I^{\pi }=3^+\) have been assigned to the \(^{182}\)Ir ground state from internal conversion electron measurements to prepare atomic spectroscopy studies in the Ir isotopic series.

abstract

In the presented report the perspectives of the study of the electric charge and current space distributions in the nuclei by laser spectroscopy methods on the beams of the fast multiple charged ions are discussed. The calculations of both the level energies and widths in the H-like and He-like ions and of the isotopic shifts and hyperfine splitting in the optical spectra of these ions are performed . The project of the experimental set-up for these measurements is considered.

abstract

The method of laser induced resonance fluorescence on an atomic beam has been used in order to measure hyperfine structure splittings of the \(4f^7 6s^2\;{}^8{\rm S}_{7/2}\) and \(4f^7 6s6p\;{}^6{\rm P}_{5/2}\) levels of the unstable isotope \(^{155}\)Eu. Experimental values of magnetic-dipole \(A\)- and electric-quadrupole \(B\)-constants of \(^{155}\)Eu have been determined for the first time; \(A_{\rm exp}({}^{155}\)Eu\({}^8{\rm S}_{7/2})=-8.87(22)\) MHz, \(A_{\rm exp} ({}^{155}\)Eu\({}^6{\rm P}_{5/2}) = -261(1.2)\) MHz and \(B_{\rm exp} ({}^{155}\)Eu\( {}^6{\rm P}_{5/2})\) \(= -957(12)\) MHz. After corrections for second-order hyperfine structure perturbations the values: \(A_{\rm corr}({}^{155}\)Eu\({}^6{\rm P}_{5/2}) = -260.9(1.2)\) MHz and \(B_{\rm corr}({}^{155}\)Eu\({}^6{\rm P}_{5/2})=-958(12)\) MHz have been obtained and the values of nuclear moments of 155Eu have been estimated: \(\mu ({}^{155}{\rm Eu})=1.519(10)\) n.m. and \(Q_s({}^{155}{\rm Eu})=2.512(62)\) b.

abstract

In this talk I give a brief review of the latest experimental and theoretical developments towards the understanding of the nuclear surface via ‘quasi-elastic transfer reactions’ which are among the best tools for such study since they are very localized both in energy and in impact parameter. There are also comments on how the discovery and study of the so called “halo” nuclei has changed or confirmed our previous understanding. The continuous transition towards more complicated reactions like two and multinucleon transfer and fusion is also discussed. Since the problem is still far from being solved I will try to point out the direction for further research, discussing the relative advantages and disadvantages of using reactions with light vs. heavy nuclei and low vs. high beam energies. Special attention is paid to the near to the barrier energies which are the main topic of the conference.

abstract

The multi-nucleon transfer reaction \(^{12}\)C(\(^{14}\)N,\(^{15}\)C)\(^{11}\)N was performed at 30 AMeV incident energy at GANIL to study the spectroscopy of the proton-rich, particle unstable nucleus \(^{11}\)N. Five excited levels of \(^{11}\)N are observed as well defined resonances in the spectrum of the \(^{15}\)C-ejectiles. They are localised at 2.18(5), 3.63(5), 4.39(5), 5.12(8) and 5.87(15) MeV above the \(^{10}\)C+\(p\) threshold. The comparison of the measured widths with \(R\)-matrix calculations and with positions of \(^{11}\)Be levels, allows the estimation of spins and parities for these resonances. They are respectively, 1/2\(^-\), 5/2\(^+\), 3/2\(^-\),3/2\(^-\) and 5/2\(^-\).

abstract

It is shown that the coupling of the elastic scattering channel to an elastic-transfer channel leads to a non-dispersive polarization potential with a periodic, \(l\)-dependent, energy dependence. Evidence of this is found in the elastic scattering data of \(^{12}\)C+\(^{24}\)Mg at low energies. The finding can indicate a significant \(^{12}\)C+\(^{12}\)C clustering effect in the ground state of \(^{24}\)Mg.

abstract

In \(^{178}\)Hf it has been found that some 2- and 4-quasiparticle states can occur lower in energy than members of the collective ground state rotational band with corresponding spin. Recent studies of these high-\(K\) isomers in the Lu, Hf, Ta, region have uncovered the existence of surprisingly large transition probabilities between the \(K=0\) ground state band and the high-\(K\) bands which should be forbidden if the \(K\) selection rule is valid. For the population of the \(K^{\pi }\)=8\(^-\) isomer in \(^{178}\)Hf a 2-band \(K\)-mixing model is presented which reproduces both the long lifetime of the isomer and the strong Coulomb excitation. In two scattering experiments at the Munich tandem accelerator and at the UNILAC in Darmstadt we searched for excited states built on the \(K^{\pi }\)=16\(^+\) isomer. Micro weight quantities of 10\(^{15}\) atoms in the isomeric state have been produced by a Dubna-Orsay-GSI collaboration in order to prepare a radioactive target. In both measurements the first excited state built on the \(K^{\pi }\)=16\(^+\) isomer has been observed at an excitation energy of 357 keV with respect to the isomeric state. The intrinsic electric quadrupole moment of \(Q_0=8.2 \pm 1.1\) b has been derived from the experimental data within the rigid rotor model.

abstract

The fission probability has been measured in the \(^{233}\)U\((d,pf)^{234}\)U reaction as a function of the excitation energy. Octupole rotational bands have been identified with rotational parameters of \(\hbar ^2/2\theta \) = 2 keV, which is characteristic to the hyperdeformed nuclear shape.

abstract

Analysis of inclusive nonelastic nucleon emission use inconsistently gradual absorption into the quasibound particle-hole states of multistep compound reaction chain together with the predominantly onestep direct reactions to describe experiments [1–3]. A sum rule analysis of the onestep direct reactions cross section calculated in the framework of the multistep direct reaction theory of Feshbach, Kerman and Koonin (FKK) [4] has revealed that these cross sections are misinterpreted.

abstract

We have performed a number of high precision measurements of cross sections and polarisation observables in \(p\)-\(d\) scattering from \(E_p\) = 245 keV to the breakup threshold. We observed very good agreement between experiment and calculations for the cross sections and tensor analysing powers while a discrepancy for vector analysing power persists and increases with decreasing beam energy. We demonstrated that current three nucleon forces cannot account for this puzzling observation and suggest that the origin of the discrepancy is either due to the inadequacies of \(NN\) potential models or, more likely, to the existence of a new type of three body force. We also confirmed for the first time the existence of a theoretically predicted pole in the doublet \(S\)-wave effective range function.

abstract

Two-dimensional proton–proton \((pp)\) and proton–proton–neutron \((ppn)\) coincidence spectra from d + d reaction were calculated, taking into account quasi free scattering (QFS) of protons and final state interaction (FSI) of neutron–proton pairs. Deuteron beam energy \(E_0 = 46.7\) MeV, proton emission angles \(\vartheta _{1} = \vartheta _{2} = 38.75^\circ \), \(\varphi _{1} - \varphi _{2} = 180^\circ \) and a neutron one \(\vartheta _{n} = 0^\circ \) are the pp QFS kinematic conditions. The results are compared to appropriate experimental data. Contribution from singlet deuterons disintegration seems to prevail in coincidence spectra and about one fourth part of all coincidence events is from pp QFS.

abstract

Even at low energies the study of the reactions occurring in the interaction of two heavy ions reveals a large variety of contributing mechanisms. The complete fusion of the two ions is usually the dominant process, but even at energies only slightly greater than the Coulomb barrier incomplete fusion and deep inelastic processes are far from being negligible. Contrary to a widespread opinion the complete fusion itself may not produce immediately an equilibrated compound nucleus. On the way to the equilibrium the emission of pre-equilibrium ejectiles from the intermediate composite nucleus created in the fusion may be measurable. From its study one may deduce important information on both the two ion mean field interaction and the intranucleon interaction cascade through which the composite nucleus equilibrates. Meaningful information on these phenomena has been obtained by activation studies by measuring the excitation functions for residue formation, residue forward range recoil distributions and mean forward ranges, and residue angular distributions. As an example of such studies I will discuss the results of a study of the interaction of \(^{12}\)C and \(^{16}\)O with heavy nuclei showing how the observations mentioned above may lead to a quite accurate determination of the cross-sections of the contributing mechanisms, and provide information on the fragmentation of the projectile and the emission of fast ejectiles during the composite nucleus thermalization.

abstract

Several co-existing models of pre-equilibrium cluster (complex particle) emission are currently in use. They are quite different in their physical assumptions, but in some cases they yield rather close results. We apply current pre-equilibrium models to the isotopic effect of (n,\(\alpha \)) reactions and illustrate some possible future modifications of the existing models for the complex particle emission.

abstract

The Dinuclear System Concept (DNSC) is developed for the description of complete fusion of nuclei. The DNSC is based on the information on the interaction of two nuclei in the deep inelastic collision which have been obtained in the study of deep inelastic transfer reactions. The DNSC revealed the new aspects of complete fusion of massive nuclei: the specific inner fusion barrier \(B^*_{\rm fus}\) and the competition between complete fusion and quasi-fusion. The DNSC is used for the analysis of reactions of heavy and superheavy element synthesis.

abstract

The results presented in this paper clearly suggest that a coherent framework may exist which connects the topics of heavy-ion molecular resonances, hyperdeformation effects, and fission shape isomerism. New data on particle-particle-\(\gamma \) triple coincidences of the \(^{28}\)Si+\(^{28}\)Si reaction at a beam energy corresponding to the population of a conjectured J\(^{\pi }\) = 38\(^{+}\) resonance in \(^{56}\)Ni are presented. The absence of alignment of the spins of the outgoing fragments with respect to the orbital angular momentum is found to be in contrast with the alignment as measured for the \(^{24}\)Mg+\(^{24}\)Mg resonances. A molecular-model picture is presented to suggest a “butterfly” motion of two oblate \(^{28}\)Si nuclei interacting in a equator-to-equator molecular configuration.

abstract

We check the consistency of methods proposed to extract fusion barriers directly from the experiment. Although the methods give acceptable results we show that this task requires a great precision on the data.

abstract

Nuclear fusion at energies close to the Coulomb barrier emphasises interesting features of the interplay between reaction mechanisms and nuclear structure \cite {row}. Both static and dynamical deformations of the target and projectile give rise to a range of Coulomb barriers depending on the orientation of the colliding nuclei, in the case of a rotational target, or the induced dynamical deformation in the vibrational case. In the vibrational, and almost symmetric, \(^{58}\)Ni+\(^{60}\)Ni system, a well defined discrete barrier distribution has been found \cite {leigh}. This distribution is explained by strong multi-phonon couplings between the colliding nuclei. This interpretation of the fusion data led us to predict that an experiment performed at several energies covering the barrier distribution could reveal previously unobserved features of the spin distribution, including a spin population of the evaporation residues up to about 20 \(\hbar \), even 5 MeV below the conventional Bass barrier. Fusion of \(^{58}\)Ni with \(^{60}\)Ni at three near and sub-barrier energies has been studied in Strasbourg with a \(^{58}\)Ni beam from the VIVITRON accelerator on thin \(^{60}\)Ni targets, leading to the \(^{118}\)Ba* compound nucleus. The \(\gamma \)-rays of the evaporation residues were identified in the GAREL+ array. Proton-rich isotopes of I, Xe, Te and Sb were observed, some up to spins of 30 \(\hbar \). A study of the relative population of these nuclei is presented and compared with calculations which accounts for of the correct barrier distribution.

abstract

The investigations of the decay properties and formation cross sections of the heaviest isotopes of the 110 and 112 elements with atomic numbers 276, 277 and 282, 283, respectively, were performed at the FLNR JINR with the use of the intense internal and extracted \(^{48}\)Ca beams. \(^{232}\)Th and \(^{238}\)U targets were used for the experiments. With the use of \(^{238}\)U target at the beam energy \(E_{\rm targ.}\) = 231\(\pm \)3 MeV (E\(^{*}\) = 31 MeV) two spontaneous fission events were detected, that corresponds to the cross section — 5.0 \(\pm \) 2 pb. The result could be explained as spontaneous fission of the even–odd isotope \(^{283}\)112 with half life \(T_{1/2}\) = 117\(^{+283}_{-48}\) seconds. The probability of \(\alpha \) decay of \(^{283}\)112 is not excluded and the possible branching ratio could be b\(_{\alpha }\) \(\approx \) b\(_{\rm sf}\) \(\approx \) 50 %.

abstract

Stability of transactinide nuclei is discussed. Theoretical results were obtained in a multidimensional deformation space on the basis of the macroscopic-microscopic model. In the large enough deformation space, shell closures at \(Z=108\) and \(N=162\) were obtained which stabilize the recently synthesized deformed superheavy nuclei. Much stronger influence of the shells at \(Z=114\) and \(N=184\) on the calculated half-lives for spherical superheavy nuclei is also demonstrated.

abstract

Nuclear density fluctuations are introduced into BUU simulations of reactions between heavy ions. In cases of spinoidal instabilities of the interacting systems they strongly enhance a production of light and intermediate mass fragments.

abstract

Langevin equations are used to model many processes of physical interest, including low-energy nuclear collisions. We develop a general method for computing probabilities of very rare events (e.g. small fusion cross-sections) for processes described by Langevin dynamics. As we demonstrate with numerical examples, our method can converge to the desired answer at a rate which is orders of magnitude faster than that achieved by using direct simulations of the process in question.

abstract

Solid state physics with radioactive atoms employs nuclear techniques like Mößbauer Spectroscopy, Perturbed Angular Correlation, \(\beta \)-NMR and Emission Channeling as well as tracer techniques like Radiotracer Diffusion or radioacitve Deep-Level Transient Spectroscopy, Capacitance-Voltage measurements, Hall-effect measurements or Photoluminescence Spectros- copy. Different problems are attacked in metals, semiconductors and superconductors, while defects and impurities in semiconductors still represent the main field of activities. Several possibilities exist to dope samples with radioactive isotopes, ranging from diffusing commercially available radioisotopes such as \(^{111}\)In into the host lattice up to on-line implantations at ISOLDE/CERN. The paper will give some examples for different types of experiments.

abstract

The energy and particle intensity domain of the CRYRING heavy-ion accelerator is well suited for studies of Single Event Upset phenomena. This effect occurs when a charged particle hits a working electronic circuit and the charge created alters its state. The radiative environment is one of the major problems for electronic circuits in an orbiting satellite. The situation is similar for future detectors at the new high-energy physics facilities, like the Large Hadron Collider (LHC) at CERN. The increasing use of submicron technology in combination with a lowering of the circuit voltage decreases the critical charge for temporary upsets. In this article the SEU test setup at CRYRING is described, where memories are used for testing digital circuit technologies. For these tests two types of particle extraction is used and two types of scintillator beam monitors (BaF\(_2\) and YAP) are described. Temporary, soft errors were recorded in static RAM memory circuits.

abstract

Isostructural oxide single crystals of the fluorite structure: stabilized cubic zirconia and UO2 were bombarded at room temperature with 72 MeV iodine ions or 340 MeV Xe ions, respectively. The aim of this paper was the study of structural transformations induced by ion bombardment in two different regimes: at 72 MeV where the radiation damage production is strongly influenced by collision cascades and at higher energies where the ionization mechanism prevails. The structure of as-grown and implanted single crystals was examined using the RBS/channeling technique and X-ray diffraction analysis. Some of the samples were also investigated by transmission electron microscopy. It was observed that the residual damage depends strongly on energy loss mechanism, and hence on the incident ion energy. At high incident energies solidification of latent tracks in UO\(_{2}\) leads to their polygonisation. Since the energy of 72 MeV is too low for latent track formation, the resulting damage is composed of dislocation and clusters and is similar to that created by the ion bombardment at low energies. The amount of defects was strongly enhanced by the interaction of ionised regions with collision cascades.

abstract

Positron Emission Tomography (PET) is a method for determining biochemical and physiological processes in vivo in a quantitative way by using radiopharmaceuticals labelled with positron emitting radionuclides as \(^{11}\)C, \(^{13}\)N, \(^{15}\)O and \(^{18}\)F and by measuring the annihilation radiation using a coincidence technique. This includes also the measurement of the pharmacokinetics of labelled drugs and the measurement of the effects of drugs on metabolism. Also deviations of normal metabolism can be measured and insight in biological processes responsible for diseases can be obtained.

abstract

Accelerator mass spectrometry (AMS) is one of the most powerful applications of heavy-ion beams in fields not directly related to nuclear physics basic research. The development of this highly sensitive technique at the electrostatic accelerator of the TANDAR laboratory has recently been accomplished. Aiming at environmental applications of our AMS activities, we have established a research program using the long-lived radioisotope \(^{36}\)Cl as an atmospheric tracer, in cooperation with the AMS group of the Technical University of Munich. The subject of the investigation was the global fallout of \(^{36}\)Cl and its latitudinal distribution. Precipitation samples were collected at different latitudes in Argentina, Chile, and Antarctic, covering a range from 24\(^\circ \)S to 62\(^\circ \)S. The resulting \(^{36}\)Cl/Cl ratios varied from \(1 \times 10^{-14}\) to \(62 \times 10^{-14}\). Systematics studies of this radioisotope may provide a monitor for atmospheric releases (anthropogenic contribution) and a baseline for natural \(^{36}\)Cl concentration.

abstract

The project of the future user facility Radiation Source ELBE is presented, which is being realized in the Forschungszentrum Rossendorf. After several years of intense planning, the year 1996 has brought the final approval of the project and the groundbreaking started at the end of 1997. The first electron beam is expected until the end of this decade.

abstract

Physics of nuclei at extreme values of the isospin is at the focus of present-day nuclear science. Experimentally, thanks to existing and emerging radioactive-ion-beam facilities, we are on the verge of invading the territory of extreme \(N/Z\) ratios in an unprecedented way. Theoretically, nuclear exotica represent a formidable challenge for the nuclear many-body theories and their power to predict nuclear properties far from stability. Going to the limits of the nuclear binding is also important for an improvement of our description of normal nuclei from the neighborhood of the beta stability valley. In the present talk, we review several aspects of the present-day mean-field theoretical studies of weakly bound nuclei.

abstract

The majority of the large international community in nuclear physics is looking towards the use of radioactive ion beams to broaden the horizon of our understanding of the physics of the nucleus. In theory, the use of radioactive beams will open a new era in nuclear physics by allowing access to new isotopes and by increasing the production rates of nuclei which can presently only be populated with extremely low cross-sections or not at all. However the beam intensities as well as the rather low variety of accelerated species will be constraints at least at the start up of the new facilities. A realistic physics program at SPIRAL is described as well as the necessary experimental tools. These essentially consist in two major devices built in the framework of large european collaborations: the VAMOS spectrometer and the EXOGAM \(\gamma \)-ray array.

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The mechanisms of nuclear reactions with light loosely bound projectiles (such as \(^{11}\)Be, \(^{8}\)B, \(^{11}\)Li etc.) at the near-barrier incident energy (up to 10 MeV/nucleon) were studied. The peculiarities of low energy nuclear dynamics of proton-rich ions were described in comparison with the neutron-rich and ordinary nuclei.

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Generalized version of the standard Lipkin model is presented. Parity-breaking is studied in both standard and generalized Lipkin models. The generalized Lipkin model Hamiltonian is derived from an octupole-octupole Hamiltonian. It is shown that only the generalized Lipkin model gives asymptotic zero energy splitting between the first positive and the first negative parity states for both even and odd numbers of particles as one expects in the case of octupole deformation.