Hirschegg workshop

Nuclear Structure and Dynamics at the Limits: Jan. 12 - 18, 2003

So far the following abstracts have been handed in:

At the limits: Very neutron-rich isotopes in the 132-Sn region
Oliver Arndt, K.-L. Kratz (for the IS 333, IS 378 and IS 393 ISOLDE-Collaborations)
Abstract: Using highest possible selectivity in production and detection at the CERN-ISOLDE facility, we have measured beta-decay properties of a number of new r-process isotopes in the region below and beyond doubly-magic 132-Sn. Delayed-neutron data on 129,130-Ag, 129-133-Cd, 135-In and 137,138-Sn will be compared to QRPA predictions used so far in r-process calculations.

Continuum spectroscopy of exotic nuclei
Aumann, Thomas (GSI)
Abstract: Reaction experiments with radioactive nuclei performed at GSI utilizing the Fragment Separator FRS and the LAND (Large Area Neutron Detector) reaction setup will be discussed. Nuclear reactions, e.g. one-neutron knockout, as well as electromagnetic excitations were investigated by kinematically complete measurements, i.e. coincident measurements of charged fragments, neutrons, and gamma rays. Neutron-neutron angular correlations, invariant mass spectroscopy, and momentum distributions after one-neutron knockout from two-neutron Halo nuclei give access to the ground-state properties of the projectile, but also yield spectroscopic information on the continuum states populated in the unbound (A-1) nuclei. The continuum dipole response of light neutron-rich nuclei was investigated systematically via measurements of the differential cross section for electromagnetic excitation.

Shape coexistence and low-energy excitations of exotic nuclei
Bender, M. (Service de Physique Nucl{\'e}aire Th{\'e}orique - CP229, Universit{\'e} Libre de Bruxelles, B-1050 Bruxelles, Belgium), Heenen, P.-H. (Service de Physique Nucl{\'e}aire Th{\'e}orique - CP229, Universit{\'e} Libre de Bruxelles, B-1050 Bruxelles, Belgium)
Abstract: Recent experimental data on stable and exotic nuclei exhibit a rich variety of new phenomena like shape coexistence and shell quenching which often cannot be described and explained on the basis of even the best available mean-field models. For their reliable description it is inevitable to go beyond the mean-field approach and include correlations into the modeling. Starting from the self-consistent Skyrme-mean-field model, we perform configuration-mixing calculations by means of the generator coordinate method of angular-momentum and particle-number projected mean-field states to investigate collective low-energy excitations throughout the chart of nuclei. Examples of results on shape coexistence phenomena will include even-even nuclei around $^{74}$Kr and $^{186}$Pb.

Two-proton emission from proton drip-line nuclei
B. Blank, CEN Bordeaux and Argonne National Laboratory
Abstract: Recent results on the two-proton radioactivity of Fe45 from GANIL and GSI will be presented, which show the first evidence of this new radioactivity. Beyond the present results, future studies will be discussed. In a second part, new results on two proton emission from excited states in Ne17 will be presented. In these complete kinematics measurements, the angle between the two protons has been measured evidencing a He2 emission pattern.

First-forbidden decays near the r-process paths
I.N. Borzov (IPPE, Obninsk)
Abstract: The $\beta$--decay rates for very neutron-rich nuclei relevant to the r-process nucleosynthesis are mostly beyond experimental reach. Their predictions demand a self-consistent extrapolation of various nuclear properties away from the experimentally known regions. The sole consideration of the allowed transitions commonly used in large-scale microscopic calculations also needs to be revised in different mass regions. The density functional+continuum QRPA approximation to self-consistent calculations of the ground state properties, Gamow-Teller and first-forbidden $\beta$--decay transitions of nuclei far from stability is developed. Systematic calculations are performed of the allowed and first-forbidden $\beta$--decay rates for the r-process relevant nuclides near the closed neutron shells at N=50,82,126. The importance of first-forbidden decays near Z$\geq$50, N$\approx$ 82 and near N=126 is shown. Possibility of the $\beta$--decay near exotic shell closure of Z=50, N=126 is discussed. The total $\beta$--decay half-lives in the region "east" of the $^{208}$Pb are estimated. A comparison of the results with recent experimental data, global calculations and self-consistent microscopic predictions is present

Nuclear Astrophysics with the DRAGON Facility at TRIUMF-ISAC: Latest results
John M. D'Auria (Simon Fraser University) and the DRAGON Collaboration
Abstract: The DRAGON facility at the new intense radioactive beams facility, ISAC, is now operational. Built to performed studies of radiative capture reaction involving radioactive reactants, and of interest to nuclear astrophysics, DRAGON has been used to performed a study of the 21Na(p,g)22Mg reaction using inverse kinematics. Resonance strengths have been measured for key states in 22Mg. In this presentation details of the facility and the commissioning studies that have been performed will be described along with aspects of this particular study and the impact of the results. A general overview of the ISAC and the new ISAC II facilities will also be mentioned.

Alpha-decay branching ratios of near-threshold states in $^{19}$Ne and the astrophysical rate of $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne
Davids, B. (KVI), van den Berg, A.M. (KVI), Dendooven, P. (KVI), Fleurot, F. (KVI), Hunyadi, M. (KVI), de Huu, M.A. (KVI), Rehm, K.E. (Argonne), Segel, R.E. (Northwestern University), Siemssen, R.H. (KVI), Wilschut, H.W. (KVI), W\"{o}rtche, H.J. (KVI), and Wuosmaa, A.H. (Argonne)
Abstract: The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is one of two routes for breakout from the hot CNO cycles into the $rp$ process in accreting neutron stars. Its astrophysical rate depends critically on the decay properties of excited states in $^{19}$Ne lying just above the $^{15}$O + $\alpha$ threshold. We have measured the $\alpha$-decay branching ratios for these states using the $p(^{21}$Ne,$t)^{19}$Ne reaction at 43 MeV/u. Combining our measurements with previous determinations of the radiative widths of these states, we conclude that no significant breakout from the hot CNO cycle into the $rp$ process in novae is possible via $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne, assuming current models accurately represent their temperature and density conditions.

Density matrix renormalization group: a new method for large scale shell model calculations
J. Dukelsky and S. Pittel (Instituto de Estructura de la Materia. CSIC Madrid)
Abstract: Large scale diagonalization is an essential tool to describe the physics of strongly correlated finite Fermi systems like molecules, clusters, grains, quantum dots, atomic nuclei, etc. The algorithms of Lanczos and Davidson have made it possible to obtain the exact low lying eigenstates of matrices up to dimensions of $\sim 10^7$. By exploiting all possible symmetries, the present shell model codes can deal with nuclei part way through the f-p shell. Going beyond these stringent limits inevitably involves the use of an efficient truncation strategy. The density matrix renormalization group (DMRG) has emerged in ondensed matter theory as a powerful tool to study the physics of low dimensional systems. The DMRG is an iterative truncation procedure for selecting in an optimal manner a manageable valence space. Recently, there have been several attempts to apply the DMRG to finite Fermi system. In this talk we first introduce the basic concepts of the DMRG, then describe some preliminary applications to nuclear schematic models and discuss the general procedure we believe feasible for nuclear structure studies of heavy nuclei.

Spectroscopy of exotic nuclei using knockout reactions
Enders, J. (TU Darmstadt/NSCL/MSU), Bazin, D. (NSCL/MSU), Glasmacher, T. (NSCL/MSU), Hansen, P.G. (NSCL/MSU),\\ Sherrill, B.M. (NSCL/MSU)
Abstract: Direct knockout from fast ($\ge$50 A MeV) ion beams is being developed as a versatile, reliable, and very sensitive spectroscopic tool. Knockout reactions allow one to determine key information, such as quantum numbers, absolute shell occupancies, and energies of excited levels especially in exotic nuclei far from stability. The reaction residues in these experiments are identified and momentum analyzed in a high-resolution magnetic spectrograph in coincidence with position-sensitive gamma-ray detectors. Recent results obtained at the National Superconducting Cyclotron Laboratory will be presented.

Nuclear structure with realistic potentials
Neff, T. (GSI), Feldmeier, H. (GSI)
Abstract: We present a unitary correlation operator that explicitly induces into shell-model type many-body states short ranged two-body correlations that are caused by the strong repulsive core and the pronounced tensor part of the nucleon-nucleon interaction. Alternatively an effective Hamiltonian can be defined by applying this unitary correlator to the realistic nucleon-nucleon interaction. The momentum space representation shows that realistic interactions which differ in their short range behaviour are mapped on the same correlated Hamiltonian, indicating a successful provision for the correlations at high momenta. Calculations for 4He using the one- and two-body part of the correlated Hamiltonian compare favorably with exact many-body methods. The need to introduce three-body forces in order to correct the underbinding of realistic interactions is also seen in heavier nuclei like 16O and 40Ca where exact many-body calculations are not possible. The Unitary Correlation Operator Method applied to the single-particle momentum distribution describes also the occupation of states above the Fermi momentum. It can be used in mean-field and shell-model configuration spaces that are not able to describe these repulsive and tensor correlations explicitly.

Shell structure from N=Z ($^{100}$Sn) to N$\gg$Z ($^{78}$Ni)
H. Grawe (GSI)
Abstract: The shell structure of $^{100}$Sn as inferred from in-beam $\gamma$-ray spectroscopy and $\beta$-decay studies at ISOL and in-flight separators shows close resemblance to $^{56}$Ni one major shell lower. The results of large-scale shell model calculations employing realistic interactions derived from effective NN potentials by G-matrix theory will be confronted with experimental evidence from Gamow-Teller decay and in-beam data with emphasis on seniority and spin-gap isomers, and core excitations. Key examples from recent experiments are $^{94}$Ag, $^{98}$Cd and $^{102,103}$Sn. The dominant monopole interaction of the spin-flip partners $\pi g_{9/2} - \nu g_{7/2}$ in N=50,51 isotones below $^{100}$Sn is echoed in the $ \pi f_{5/2} - \nu g_{9/2}$ pair of nucleons, which is decisive for the N=50 shell gap in $^{78}$Ni. The persistence of the N=50 shell and the weakness and extreme locality of the N=40 shell in $^{68}$Ni can be traced back to monopole driven migration of selected single particle orbits. Recent experimental data on $^{70,72,76}$Ni, $^{78}$Zn and $^{67}$Fe give supportive evidence for this scenario, which can be generalized to explain new shell structure in light and medium-heavy neutron-rich nuclei.

Theory of two-proton decay and prospective candidates for experimental studies
L.V. Grigorenko ( GSI, Planckstr. 1, D-64291 Darmstadt, Germany), I.G. Mukha (GSI), and M.V. Zhukov (Chalmers Univ. of Tech., S-41296 Geteborg, Sweden)
Abstract: In paper [L.Grigorenko et al., Phys. Rev. Lett. 84, 1116 (2000)] a three-body cluster model has been developed for studies of the two-proton (and more generally three-body) decays. The model allows to calculate lifetime dependencies on the decay energy and momentum distributions among fragments. The model have been tested on the number of light systems, where sufficient experimental information is available, like $^6$Be, $^8$Li, $^9$Be, $^{12}$O, and $^{16}$Ne. Interesting structure effects, which were characterized as a three-body mechanism of the Thomas-Ehrman shift, have been predicted for $^{12}$O and $^{16}$Ne [L.Grigorenko et al., Phys. Rev. Lett. 88, 042502 (2002)]. In our recent work [L.Grigorenko et al., NPA, in press] we have performed exploratory studies of the prospective two-proton decay candidates: $^{19}$Mg, $^{30}$Ar, and $^{34}$Ca. The results of the studies show that a special experimental technique (in-flight decay) could be required to measure their lifetimes. The recent discovery of the two-proton decay of $^{45}$Fe is discussed. We extensively compare the three-body quantum mechanical calculations with various forms of quasiclassical estimates aiming qualitative understanding of the phenomenon.

Masses of nuclei close to the drip-line
Herfurth, F (CERN), Audi, G (CSNSM), Beck, D (GSI), Blaum, K (CERN), Bollen, G (NSCL), Kellerbauer, A (LMU), Kluge H.-J. (GSI), Lunney, D (CSNSM), Moore, R.B. (McGill), Schwarz, S (NSCL), Sikler, G (GSI), Weber, C (GSI)
Abstract: The mass is one of the gross properties of a nucleus. The mass, explored over large areas, helps the understanding of the nucleus considerably by revealing weaknesses in nuclear models, by uncovering nuclear fine structure effects as well as shell closures. At the drip-line, known or predicted mass differences help to find especially interesting decay modes as for instance the double proton decay. Naturally, drip-line nuclei have very short half-lives. This explains why direct mass determination techniques can only access a small fraction of these nuclei. However, accurate direct techniques as for instance Penning trap mass spectrometry together with reaction and decay energy measurements provide mass values for nuclei at the drip-line and beyond as demonstrated in the rare earth region. By using the improved Penning trap mass spectrometer ISOLTRAP/CERN, it is even possible to measure masses with relative uncertainties as low as $10^{-7}$ in the direct vicinity of the drip-line. Recent examples are the mass measurements of $^{74}$Rb, $^{32}$Ar or $^{72}$Kr.

Conversion electron spectroscopy around Z=100
Herzberg, R-D (University of Liverpool)
Abstract: One of the unique challenges in the spectroscopy of superheavy nuclei is given by the large internal conversion coefficients typically found in very heavy, highly charged systems. In Fermium nuclei (Z=100) any E2 or M1 transition below $\sim 200$ keV and $\sim 400$ keV respectively will proceed predominantly by internal conversion rather than the emission of gamma rays. The SACRED spectrometer [1] has been coupled to the gas-filled separator RITU [2] of the University of Jyv"askyl"a in near-180-degree geometry to allow in-beam recoil decay tagging studies of fermium and transfermium nuclei. Successful experiments on ${}^{250}$Fm [3] and ${}^{254}$No [4] have been performed using this combination. The results of these studies indicate a large population of an isomeric state in both nuclei. [1] P.A Butler et al., Nucl. Instr. Meth. A 381 (1996) 433.\\{} [2] M. Leino et al., Nucl. Instr. Meth. B 99 (1995), 653.\\{} [3] R-D Herzberg et al., Proceedings of the Conference "Frontiers of Nuclear Structure", Berkeley, USA, 29.7-2.8.02.\\{} [4] P.A Butler et al., Phys. Rev. Lett. 89, (2002), 202501.

On the Synthesis of New Elements
Hofmann, S. (GSI Darmstadt)
Abstract: The nuclear shell model predicts that the next doubly magic shell-closure beyond 208Pb is at a proton number between Z = 114 and 126 and at a neutron number N = 184. The outstanding aim of experimental investigations is the exploration of this region of spherical 'Superheavy Elements'. An overview will be given of recent studies of the properties and synthesis of these superheavy elements.

Decay studies of neutron-rich Po, Bi and Pb isotopes
Mark Huyse for the IS387 ISOLDE collaboration
Abstract: The region around doubly-magic 208Pb is an ideal testing ground for the nuclear shell model and extensive research has been devoted to 208Pb and its direct neighbors. Also the region west of it, emptying the N=126 closed shell, has been studied with the whole arsenal of spectroscopic methods and revealed important phenomena like shape coexistence. The region east of 208Pb remained mainly untouched after the first survey in the beginning of the XXth century where the alpha-decay chains of long-lived activity were used to produce 218Po, 215Bi and 214Pb. Due to the extreme N to Z ratio, these nuclei east of 208Pb are hardly accessible with light- or heavy-ion induced fusion reaction and therefore the only possibility to produce them is to fragment heavier actinide targets or beams. Recently the projectile fragmentation of 1000 MeV/u 238U in combination with in-flight separation has been used to study nine known and 4 new microseconds isomers in the trans-lead region [Pfü98]. Copious amounts of neutron-rich Po, Bi and Pb nuclei are produced in the Th and U targets of the ISOLDE separator by spallation with a 1 GeV proton beam. But detailed decay studies were till now impossible due to the fact that their isobars in the At to Ac region are strongly contaminating the spectra as these isobars are orders of magnitude more produced. Two novel techniques, recently developed at ISOLDE, have led to the production of relative pure beams of neutron-rich Po, Bi and Pb nuclei and enabled detailed decay studies. The first technique is related to the release time of the different species out of the target and cuts away the micro- to milliseconds activity of the alpha-decaying isobars by closing the mass separator during the proton pulse and shortly after [Van98]. The second technique relates to the ion source and uses laser light to resonantly ionize the elements of interest [Kös02]. These two methods and their implication on possible decay studies will be discussed. A survey of the recent results on the new 216, 217, 218Bi and 215Pb nuclei, together with extended information on a number of lighter Po, Bi and Pb nuclei, will be given. The talk will conclude with an outlook on further possibilities for decay studies. [Pfü98] M. Pf\"utzner et al., Phys. Lett. B444 (1998) 32 [Van98] P. Van Duppen et al., Nucl. Instr. Meth. B134 (1998) 32 [Kös02] U. K\"oster, Nucl. Phys. A701 (2002) 441c

The transport coefficients for fusion-fission reactions. Influence of shells, pairing, rotation.
Ivanyuk,F.A. (GSI, Darmstadt) and Hofmann,H (TUM, Munich)
Abstract: We study the collective motion of isoscalar type at finite excitations. The collective variables are defined as the shape degrees of freedom and the mean field is approximated by deformed shell model potential. The transport coefficients of the slow collective motion (friction coefficient, mass parameter, stiffness of the potential energy) are defined within the linear response theory and locally harmonic approximation. We pay the special attention to the case of low excitation energies, where the shell effects and pairing correlations are important. As an application of the theory the numerical results for the deformation energy and the tensors of friction and inertia are presented for few composite systems formed in fusion reactions used for the synthesis of super-heavy elements. It is demonstrated that the dissipation decreases with decreasing temperature and growing pairing gap and falls well below the values of common "macroscopic models". The comparison of the fission times computed with the "macroscopic" and "microscopic" transport coefficients shows that they differ by the order of magnitude. Both friction and inertia show a sensible dependence on the configuration of the mean field caused both by the shell effects as well as by avoided crossings of single-particle levels. The semianalytical expressions are suggested for the temperature dependence of those combinations of the transport coefficients which govern the fission process. The influence of rotation on the potential energy and transport coefficients of the collective motion is examined. We have found out that at excitation corresponding to the temperatures T < 1 MeV the shell correction to the liquid drop energy practically does not depend on the angular rotation. The friction and the mass parameters are rather stable to the nuclear rotation provided that the contributions to the spurious states arising due to the violation of rotational symmetry are removed.

An experimental measure of the phase diagram of bulk nuclear matter
Elliott, J.B. (Lawrence Berkeley National Labortory), Moretto, L.G. (Lawrence Berkeley National Labortory), Phair, L. (Lawrence Berkeley National Labortory), Wozniak, G.J. (Lawrence Berkeley National Labortory)
Abstract: Recent developments in the analysis of nuclear multifragmentation and compound nuclear decay data resulted the determination of the pressure-density-temperature phase diagram of bulk nuclear matter, establishing the boundaries of the nuclear liquid and vapor. The phase diagram was constructed by using a well known condensation model for normal fluids, modified to account for the Coulomb and symmetry energies present in nuclei, to describe the fragment distributions from several different experiments. The free parameters in the condensation model, e.g. the surface energy coefficient and energy of vaporization, agree well with the standard values of the nuclear liquid-drop model. Using finite size scaling techniques, the bulk property of nuclear matter was extracted from the behavior of finite, charged samples of nuclear matter, i.e. nuclei, and the pressure-density-temperature phase diagram of bulk nuclear matter was constructed.

In-Beam Spectroscopy of Very Heavy Elements
Julin, R. (University of Jyväskylä)
Abstract: The anomalously high production cross-section of about 2 mb for the cold fusion reaction 208Pb(48Ca,2n)254No was utilized in the in-beam g-ray studies of 254No, where the Gammasphere array was combined with the Fragment-Mass-Analyzer (FMA) at Argonne [1] and the Ge clover array (SARI) was combined with the RITU-gas-filled-separator at Jyväskylä [2]. By employing the recoil- gating and recoil-decay-tagging techniques the yrast line of 254No was identified revealing a deformation parameter, b2 , of 0.27(2) in good agreement with predictions. Following this success, the Jurosphere2 array + RITU system was employed in a similar in-beam study of 252No for which the production cross-section in the 206Pb(48Ca,2n) reaction is only 300nb [3]. The yrast rotational band of 252No was observed up to Ip = 20+ indicating that 252No is less deformed than 254No and showing evidence for quasiparticle alignment. Both the 254No and 252No data reveal that the fission barrier exists at least up to I $\sim$ 20 in these nuclei. In order to gain experimental knowledge of single-particle states in heavy nuclei the next in-beam recoil-tagging experiment in Jyväskylä was focused on 255Lr and in Argonne on 253No. They were produced via the 209Bi(48Ca,2n) and 207Pb(48Ca,2n) reactions, with cross-sections of about 300nb and 500nb, respectively. Strong X-ray peaks in the resulting spectra indicate that the decay along the yrast line of these nuclei proceeds by strongly converting M1 transitions, which calls for electron-spectroscopic methods. In the present contribution, the results obtained at Jyväskylä will be discussed in more detail. Plans and limitations of similar in-beam experiments with improved systems will be discussed. [1] P. Reiter et al., Phys. Rev. Lett. 83, 1108 (1999) [2] M. Leino et al., Euro. Phys. Jour. A6, 63 (1999) [3] R.-D. Herzberg et al. Phys. Rev. C65, 014303 (2002).

Spin-orbit and spin-spin interaction in intermediate mass hypernuclei
C. Keil, H. Lenske
Abstract: The spin-orbit interaction of the $\Lambda$ hyperon is a long standing question in hypernuclear physics. By now the situation in the low mass region is due to high precision gamma spectroscopic experiments pretty much settled, confirming the extremely small spin-orbit splitting. In the intermediate and heavy mass region, however, the situation is still open. Recent data of $^{89}_\Lambda$Y and $^{51}_\Lambda$V seemed to indicate a spin-orbit splitting in the MeV range which is significantly larger than what would be expected from the light mass hypernuclei. A more subtle analysis, taking into account the high core nucleus spins of vanadium and yttrium ($6^+$ and $4^-$, respectively) and a $\Lambda$-core spin-spin interaction leads to a much smaller spin-orbit splitting and very accurately explains the data. From this information we extract within our microscopic desnity dependent relativistic hadron field theory which relates interactions in finite nuclei with free space meson exchange potentials coupling constants of the $\Lambda$ to the sigma and the omega meson. The influence of a possible $\Lambda$-$\omega$ tensor interaction is studied. Applications to recently measured $\Lambda\Lambda$ nuclei and the extraction of $\Lambda$-$\Lambda$ interactions are discussed.

Nuclear structure at the drip-line: the continuum-QRPA
Khan, E. (Institut de Physique Nucl\'eaire, Orsay, France), Sandulescu, N. (Royal Institute of Technology, Stockholm, Sweden), Grasso, M. (Institut de Physique Nucl\'eaire, Orsay,
Abstract: The nuclei close to the drip-line consists of N-body superfluid fermionic systems where the pairing and the continuum effects are strongly correlated. In order to analyze the excitations of such systems, we introduce the first RPA model which depicts the pairing and mean fields effects with an exact treatment of the continuum states. In this model, the only input remains the effective nucleon-nucleon interaction. The continuum-Quasiparticle-RPA (cQRPA) is derived in coordinate space from the linearized Time-Dependent HFB equations (TDHFB). The complete basis of the quasiparticle states is generated by a HFB calculation with an exact continuum treatment. Various results obtained with the Skyrme interaction and a zero range density dependent pairing interaction will be discussed along several isotopic chains in order to analyze the continuum effect when reaching the drip-line. The sensitivity of the nuclear excitations to the interaction will also be enlightened.

R-process signatures: observation versus model predictions
K.-L. Kratz, B. Pfeiffer, P. Möller, J. J. Cowan
Abstract: We compare astrophysical model predictions based on most recent experimental and theoretical nuclear-physics input with astronomical observations of solar system, halo-star and meteoritic r-process signatures. We deduce astrophysical conditions under which the respective isotopic or elemental r-abundance patterns can be obtained.

Slow and fast radioactive beams in study of light nuclei far from stability
Lewitowicz, M. (GANIL)
Abstract: The shell structure, well established for nuclei close to the valley of stability, is expected to evolve significantly in the presence of important excess of neutrons or protons. Nuclei in the vicinity of the drip-line exhibit particularly important changes in the intrinsic structure related to the very low binding energy and the strong influence of continuum states. In order to obtain a complete information on these effects a use of radioactive beams in the energy range from few tens of keV up to several hundred MeV per nucleon is necessary. Higher energy beams produced by an in-flight fragmentation and post-accelerated ISOL beams proved their complementarity with respect to the intensity, isotopic purity and optical quality of the beam. Both techniques currently in use at the GANIL/SPIRAL facility offer unique possibilities to make experiments with light radioactive beams (A \lt 80) in the energy range from 30keV/nucl. to $80\sim $MeV/nucl.. Relatively low intensities and high cost of radioactive beams impose in this kind of experiments a use of the most efficient detection systems. For this purpose the new high acceptance magnetic spectrometer VAMOS, the 4$\Pi$ $\gamma$-array EXOGAM and the charged particle detectors MAYA and MUST were constructed recently at GANIL by large international collaborations. Future plans of the GANIL/SPIRAL facility and in particular the SPIRAL II project will be shortly presented.

Dissolution of Shell Structures in Exotic Nuclei by Correlation Dynamics
H. Lenske, Insitut für Theoretische Physik, U. Giessen
Abstract: Exotic nuclei are ideal test cases for investigations of nuclear interactions in a strongly asymmetric medium $[1-3]$ providing us with hitherto inaccessible information on nuclear binding and dynamical processes in weakly bound nuclear matter at large isospin. In-medium interactions were studied over the full range of asymmetries up to pure neutron matter by Brueckner and Dirac-Brueckner theory and beyond the ladder approximation $[1,3]$. In-medium meson-nucleon vertices were determined $[2]$ and applied to finite nuclei with the density dependent relativistic hadron (DDRH) field theory $[2,5]$. The response of exotic nuclei to external probes was studied with non-relativistic continuum HFB and QRPA theory $[1,6]$. Calculations e.g. for the $Ni$ and $Sn$ isotopic chains $[2]$ predict for increasing neutron excess the evolution of pronounced neutron skins while bubble shapes are predicted for superheavy elements. A close connection between the nuclear equation of state and the properties of unstable nuclei is found. Dynamical properties of nuclei far off stability are investigated by (non-relativistic) RPA theory. Close to the driplines the strong increase of the nuclear polarizabilities induces a considerable amount of dynamical correlations and non-static self-energies $[1]$. As an important consequence the dominance of mean-field dynamics is suppressed and shell structures are dissolved. Core polarization becomes the dominant binding mechanism in the single nucleon halo systems $^8$B, $^{11}$Be and $^{19}$C. The binding of the two-neutron halo nucleus $^{11}$Li is determined almost exclusively by pairing interactions. The wave functions are applied in low-energy transfer reactions and break-up processes at relativistic energies $[6]$. Results for the longitudinal momentum distribution from the breakup are compared to GSI/FRS data [6]. {\footnotesize {\bf References:}\ $[1]$ H. Lenske, F. Hofmann, C.M. Keil, Rep.Prog.Nucl.Part.Phys. 46 (2001) 187; e-Print Archive: nucl-th/0012082\ $[2]$ F.Hofmann, C.M. Keil, H. Lenske, Phys.Rev. C64:025804 (2001), nucl-th/0008038\ $[3]$ F.Hofmann, C.M. Keil, H. Lenske, Phys.Rev. C64:034314 (2001), nucl-th/0007050\ $[4]$ C.M. Keil, F. Hofmann, H. Lenske, Phys.Rev. C61 (2000) 064309, Phys.Rev. C (2002) (in print)\ $[5]$ C. Fuchs, H. Lenske, H. Wolter, Phys.Rev. C52 (1995) 3043\ $[6]$ D. Cortina-Gil et al., Eur.Phys.J A10 49 (2001);C. Gund, Eur.Phys.J A10 (2001) 85; F. Cappuzzello, Phys.Lett. B516 (2001) 21; D. Cortina-Gil et al. Phys.Lett. B 529 (2002) 36.}

Isospin symmetry in medium-light nuclei
Lenzi, S.M. (Universty of Padova)
Abstract: One of the challenges of modern nuclear physics is the exploration of the limits of validity of the isospin symmetry for increasing values of Z. Within its limits of validity, the symmetry itself can be exploited to reveal details on nuclear structure features. The breakdown of the symmetry due to the Coulomb field and isospin non conserving terms in the nuclear interaction increases with Z and is maximum at the N=Z line due to the increasing overlap of the proton and neutron wave functions. The limits of validity of the isospin symmetry is very important when mapping the proton drip line to determine the rp process. Recent experimental and theoretical investigations of isospin symmetry along the N=Z line in medium-light nuclei will be presented. In particular, the isospin mixing in the N=Z 48Cr nucleus measured with Euroball will be discussed. Other interesting results concern the Coulomb energy differences in mirror nuclei in the f7/2 shell, interpreted by means of large scale shell model calculations, which show the evidence of the isospin non conserving terms of the nuclear potential.

Weak-interaction processes in stars
Martemnez-Pinedo, G. (IEEC/ICREA Barcelona)
Abstract: Recent advances in nuclear structure modeling have lead to an improved description of astrophysically relevant weak-interaction processes. In this talk I will review this advances and discuss their application to the calculation of weak processes associated with core-collapse supernovae.

Cold Valleys in Fission and Fusion
Serban Misicu (University of Frankfurt)
Abstract: The cold fission configuration after the preformation of the fragments resembles a short-lived dinuclear or quasi-molecular system. The most conceivable scission configuration is given by two fission fragments in touching with the symmetry axes aligned (pole-pole orientation). This conclusion was based on the simple argument that this configuration offers the optimal tunneling time, i.e. the difference between the Coulomb barrier and the decay energy $Q$ is minimal. Other orientations are apparently precluded in cold spontaneous fission. The pole-pole orientation gives the best explanations of neutronless fission yields. Configurations other than the pole-pole one can be important in fusion reactions because in that case the fragments are approaching each other with various orientations and bombarding energies. It is a theoretically and experimentally almost understood fact that for fusion reactions with light and intermediate-mass nuclei the nuclear interaction is changed dramatically for certain ''orientation windows'', e.g. for flat surface area, due to strong hexadecupole deformations and, as very recently claimed, even 6-pole deformations. The way in which the superheavy elements are synthesised is no doubt also dependent on particular deformations and orientations. However their role is less understood. There have been theoretical claims that the equator-equator twisted orientation could be an optimal fusion configuration for the simple reason that such an orientation leads to the most compact touching configuration out of all possible orientations of two deformed. In analogy to the cold fission of $^{252}$Cf we investigate the role of the fragments deformations and orientations on the driving potential of some recently discovered superheavy elements.

Nuclear Structure at the Limits
Nazarewicz, W. (University of Tennessee)
Abstract: There are many theoretical challenges related to nuclei far from stability. Clearly, it is not ``business as usual"! In many respects, weakly bound exotic nuclei are indeed much more difficult to treat theoretically than well-bound systems. The major theoretical difficulty and challenge is the treatment of the particle continuum. The residual-interaction coupling to the continuum can influence nuclear binding, effective interaction, and core polarization. It can give rise to a new class of collective phenomena. Continuum can also dramatically influence shell structure, many-body correlations (such as pairing) and can impact the appearance of cluster structures. Consequently, many cherished approaches of nuclear theory such as the conventional shell model and the pairing theory must be modified in order to properly take into account unbound states. The main objective of this presentation is to discuss various challenges in theoretical nuclear structure, especially in the context of RNB physics. New-generation data will be crucial in pinning down a number of long-standing questions related to the effective Hamiltonian, nuclear collectivity, and properties of nuclear excitations.

Short-Ranged Central and Tensor Correlations in Nuclear Many-Body Systems
Neff, T (GSI), Feldmeier, H (GSI)
Abstract: We present a unitary correlation operator that explicitly induces into shell model type many-body states short ranged two-body correlations caused by the strong repulsive core and the pronounced tensor part of the nucleon-nucleon interaction. Alternatively an effective Hamiltonian can be defined by applying this unitary correlator to the realistic nucleon-nucleon interaction. The momentum space representation shows that realistic interactions which differ in their short range behaviour are mapped on the same correlated Hamiltonian, indicating a successful provision for the correlations at high momenta. Calculations for $^4$He using the one- and two-body part of the correlated Hamiltonian compare favorably with exact many-body methods. For heavier nuclei like $^{16}$O and $^{40}$Ca where exact many-body calculations are not possible we compare our results with other approximations. The correlated single-particle momentum distributions describe the occupation of states above the Fermi momentum. The Unitary Correlation Operator Method (UCOM) can be used in mean-field and shell model configuration spaces that are not able to describe these repulsive and tensor correlations explicitly.

Moments of neutron rich nuclei near disappearing shell closures N=8 and N=20
Neyens G (University of Leuven) in collaboration with Univ. of Leuven, Univ. Mainz, ISOLDE collaboration, GANIL, St. Kliments Ohridsky Univ. of Sofia, FLNR-JINR Dubna, Univ. Gottingen
Abstract: Neutron rich nuclei provide an interesting testing ground to study the structure of nuclei at the extremes of isospin. New nuclear structure phenomena have been discovered several years ago, such as the neutron halo structure or the disappearance of the well-known magic numbers. Although many experimental results as well as theoretical developments have been helpful in the process of understanding these structure changes, further investigations are certainly needed. In this presentation we will focus on some recent measurements of nuclear magnetic and quadrupole moments of neutron rich nuclei using spin-oriented radioactive beams. Neutron rich nuclei are well produced in projectile fragmentation reactions e.g. at GANIL, where the reaction-induced spin-orientation is maintained during the in-flight mass separation process. Also in target-fragmentation reactions at ISOLDE, CERN exotic nuclei are well produced but no spin-orientation is available in the mass-separated ion beam. Here the spin-orientation is induced using the collinear laser beams set-up COLLAPSE to polarize the radioactive beam with the optical pumping method. Results on nuclear moments of exotic nuclei obtained recently at these facilities for neutron-rich Mg and Al nuclei and neutron-rich Li- nuclei will be presented and discussed.

Study of N $\simeq$ Z krypton and strontium isotopes with a Total
Poirier E. (Strasbourg), Borge M. J. G. (Madrid), Cano-Ott D. (Madrid), Courtin S. (Strasbourg), Dessagne Ph. (Strasbourg), Fraile L. M. (Geneve), Gelletly W. (Surrey), Jungclaus A. (Madrid), Lescornet G. (Geneve), Miehe Ch. (Strasbourg), Marechal F. (Strasbourg), Nacher E. (Valence), Rubio B. (Valence), Tain J. L. (Valence) and Tengblad O. (Madrid)
Abstract: Far from stability beta decay remains one of the powerfull methods to learn about fundamental aspects of the nuclear medium and the Weak Interaction. The $N=Z$, $A \simeq 70$ region of the nuclear chart is of particular interest in regards of the rapid changes in nuclear structure. Extensive experimental works have been performed in this mass region and, in particular, theoretical calculations predict that, close to the proton drip-line, the Gamow-Teller Giant Resonance, concentrated at high excitation energy in the daughter nucleus, is accessible through $\beta$-decay studies \cite{Hamamoto93}. The influence of deformation, shape coexistence and pairing residual interaction have been extensively studied, showing in particular the effect of the shape of the ground state of the parent nucleus on the Gamow-Teller strength distribution \cite{Sarrigurren99}. In order to obtain reliable information on the complete $\beta$ strength, and therefore make valuable comparisons between experiment and theory, high resolution measurements \cite{Miehe99} together with total absorption spectrometry are necessary \cite{Algora99}. We report here on the experimental results obtained, in terms of Gamow-Teller strength and nuclear deformation, on the $^{74}$Kr and $^{76}$Sr isotopes with a new Total Absorption Spectrometer presently installed at the CERN/ISOLDE mass separator. \begin{thebibliography}{5} \bibitem{Hamamoto93} I. Hamamoto {\it et al.}, Phys. Rev. {\bf C48} 3 (1993) 2960. \bibitem{Sarrigurren99} P. Sarriguren {\it et al.}, Nucl. Phys. {\bf A691} (2001) 631. \bibitem{Miehe99} Ch. Mieh\'e {\it et al.}, Eur. Phys. J. {\bf A5} (1999) 143. \bibitem{Algora99} A. Algora {\it et al.}, Nucl. Phys. {\bf A654} (1999) 727c. \end{thebibliography}

New results on $\beta$ decay of exotic nuclei close to $^{100}$Sn: $^{94}$Ag and $^{100}$In
C. Plettner for the GSI ISOL collaboration
Abstract: Exploring nuclei in the upper proton $g_{9/2}$ shell close to $^{100}$Sn gives the opportunity to observe the phenomena generated by the residual hole-hole proton-neutron interaction, resulting in the occurrence of spin-gap isomers (e.g. $^{95}$Pd, $J^{\pi}$ = 21/2$^+$ [Nol82] and tentatively $^{94}$Ag, $J^{\pi}$ = 21$^+$) [Lac02]. Another important issue is the manifestation of the Gamow-Teller resonance in $\beta$ decay of nuclei close to $^{100}$Sn. The illustration of these topics will be given for two key-examples, investigated at the GSI on-line mass-separator: \begin{itemize} \item $^{94}$Ag is the heaviest $N = Z$ nucleus studied in detailed $\beta\gamma\gamma$ spectroscopy [Lac02]. In September 2002 we performed a considerably improved experiment compared to the earlier measurement [Lac02], using an array of Ge and Si detectors. We registered interesting coincidences between $\gamma$ rays, protons and positrons. The complex decay scheme will be presented and the existence of the tentative $J^{\pi}$ = 21$^+$ isomer which undergoes $\beta$ decay will be disscussed. \item $^{100}$In represents the proton-neutron particle-hole with respect to $^{100}$Sn and we studied its $\beta$ decay by using Ge detectors and a total absorption spectrometer. For the first time we measured a Gamow-Teller resonance so close to $^{100}$Sn [Ple02]. By measuring $\beta\gamma\gamma$ coincidences we establish the decay scheme of $^{100}$In and improved the level scheme of the daughter $^{100}$Cd nucleus. Combining the information from the experimental $\beta$ feeding and from the large-scale shell model calculations, the parity assignment of the ground state of $^{100}$In will be discussed. \end{itemize} [Nol82] E. Nolte et al., Z. Phys. A 305, 289 (1982). [Lac02] M. La Commara et al., Nucl. Phys. A 708, 167 (2002). [Ple02] C. Plettner et al., Phys. Rev. C 66, 044319 (2002).

Shell Model Description of Neutron-Rich Nuclei
Ploszajczak, M. (GANIL), Michel, N. (GANIL), Nazarewicz, W. (ORNL), Okolowicz, J. (GANIL)
Abstract: Microscopic description of neutron-rich nuclei is proposed in the Gamow Shell Model which is a generalization of a standard Shell Model in the complete basis including bound states, resonances and states of the non-resonant continuum. We shall present examples of application in the chain of Helium and Oxygen isotopes.

Synthesis of superheavy elements with $^{48}$Ca beams
A.G. Popeko, M.G. Itkis, Yu.Ts. Oganessian, V.K. Utyonkov, A.V. Yeremin
Abstract: As a result of investigations, performed in Flerov Laboratory during 1998 - 2002, in fusion reactions using the heaviest isotopes of U, Pu, Cm and Cf as targets and a $^{48}$Ca ion beam, decays of the heaviest nuclei $^{277}$Hs (Z=108), $^{280,\,281}$110, $^{283,\,284,\,285}$112, $^{286,\,287,\,288,\,289}$114, $^{290,\,292}$116 and $^{294}$118 were observed. First attempts on chemical identification of element 112, produced in the reaction $^{238}$U($^{48}$Ca,3n) were made using the gas transportation. In December 2002 we plan to repeat the $^{48}$Ca+$^{238}$U experiment with mass determination of evaporation residues and to start experiments on the synthesis of odd superheavy element 115 in $^{48}$Ca+$^{243}$Am reaction.

Effects of nuclear structure in residual nuclide production
M. V. Ricciardi, K.-H. Schmidt, P. Napolitani, A. V. Ignatyuk, F. Rejmund (GSI)
Abstract: In some nuclear reactions, the residual nuclide production is characterized by structural phenomena. The prominent structural features found in low-energy fission and in transfer reactions are related to pairing correlations and shell effects in cold nuclei which are preserved during the reaction process due to the low intrinsic excitation energy introduced. A complex fine structure has also been observed in the end products after the deexcitation of highly excited nuclei. New results deduced from the yields of residual nuclides produced in the reaction 238U + Ti at 1 A GeV are presented. The residues have been identified in mass and nuclear charge by the fragment separator at GSI. In this case, the structural features are a manifestation of condensation of pairing correlations and other phenomena in the cooling-down process at the end of the statistical deexcitation cascade. Possible relations of this structure to alpha clustering and to mean-field contributions to pairing effects are discussed.

Structure of halo nuclei - Overview of the experimental data
Riisager, K. (Inst. of Physics and Astronomy, Aarhus University)
Abstract: An overview will be given of the experimental data on halo nuclei, with emphasis on recent developments. Most of the talk is naturally concerned with reaction work, but other subjects will also be covered. Work done at European laboratories will be treated in more detail. A brief discussion of where halos might be found will serve as a bais for comments on where future developments might lead us.

The Relativistic Quasiparticle Random Phase Approximation and Applications in Exotic Nuclei.
P. Ring, T. Niksic, N. Paar, D. Vretenar.
Abstract: The relativistic quasiparticle random phase approximation (RQRPA) is formulated in the canonical single-nucleon basis of the relativistic Hartree-Bogoliubov (RHB) model. For the interaction in the ph-channel effective Lagrangians with nonlinear meson self-interactions are used, and pairing correlations are described by the pairing part of the finite range Gogny interaction. The RQRPA configuration space includes the Dirac sea of negative energy states. Both in the particle-hole and particle-particle channels, the same interactions are used in the RHB calculation of the ground state and in the matrix equations of the RQRPA. The RHB+RQRPA approach is tested in the example of multipole excitations of neutron rich oxygen isotopes. The RQRPA is applied in the analysis of the evolution of the low-lying isovector dipole strength in Sn isotopes and N=82 isotones.

Electromagnetic transitions between giant resonances within continuum-RPA
Rodin, V.A. (Institute for Theoretical Physics, University of Tuebingen), Dieperink, A.E.L. (KVI, Gronengen, the Netherlands)
Abstract: A general continuum-RPA approach is developed to describe electromagnetic transitions between giant resonances. Using a diagrammatic representation for the three-point Green's function, an expression for the transition amplitude is derived which allows one to incorporate effects of mixing of single and double giant resonances as well as to take the entire basis of particle-hole states into consideration. The radiative widths for E1 transition between the charge-exchange spin-dipole giant resonance and Gamow-Teller states are calculated for $^{90}$Nb and $^{208}$Bi nuclei. The importance of the mixing is stressed.

Spectroscopy on very neutron-rich nuclei at N=$20\sim 28$
Sakurai, H (Univ. of Tokyo)
Abstract: Recent studies on nuclear structure by using radioactive isotope beams available at the RIKEN projectile-fragment separator (RIPS) are introduced. Special emphasis is given to experiments selected from two recent programs that highlight studies, on the magicity loss observed for very neutron-rich nuclei at N$\sim$ 20, 34Mg and 30Ne, via the in-beam gamma spectroscopy, and on the particle stability of very neutron-rich nuclei, 34Ne, 37Na and 43Si. The in-beam gamma spectroscopy via several reactions has been extensively applied to observe bound excited states and to obtain nuclear properties through the excited states. The low lying excited states of 34Mg has been studied via the RI beam fragmentation method and the Coulomb excitation method. The energies of the excited states and B(E2) value obtained show that 34Mg has larger deformation than 32Mg. To increase a luminosity for weak intensity of RI beams, we are developing a liquid-hydrogen target. This target has been used to determine the energy of the first excited state of 30Ne via the proton inelastic scattering. At RIKEN, a new acceleration scheme has been applied to increase primary beam intensities. Last February, a 66 A MeV 48Ca beam was successfully accelerated with a maximum intensity of 150 pnA. This beam brought out three new isotopes, 34Ne, 37Na, 43Si, and evidence on particle instability of 33Ne, 36Na and 39Mg. All of above results would be discussed in comparison with theoretical predictions.

Mass measurements along the rp- and r-process path
Savard, G. (Argonne National Laboratory)
Abstract: The path followed in explosive astrophysical processes such as the r- or rp- processes is determined by the reaction rates and half-life of the involved nuclei, and hence critically on their masses. The CPT mass spectrometer presently in operation at Argonne allow high-precision mass measurements to be performed on isotopes with half-life exceeding 50 ms. A number of such measurements have been performed on key isotopes on the rp-process path and in the vicinity of the r-process path. These measurements will be presented together with their influence on the astrophysical processes and a brief look at future measurements in preparation.

Nuclear Astrophysics and nuclei far from Stability
Schatz, H., MSU
Abstract: I will review the important role of unstable nuclei in nuclear astrophysics. This will include a summary of recent advances in experimental nuclear physics, theoretical modeling of astrophysical scenarios, and new observations.

The isospin thermometer - a new method to determine the freeze-out temperature in fragmentation reactions
M. V: Ricciardi, K.-H. Schmdit, A. S. Botvina, T. Enqvist
Abstract: The compound-nucleus mechanism, dominating at low excitation energies, gradually changes into simultaneous decay with increasing energy. Activities have concentrated on the investigation of light clusters (multifragmentation) so far. Recently, complementary information could be extracted by studying the formation of heavy residues with a high-resolution magnetic spectrometer. Isotope yields of heavy residues produced in collisions of 238U and 208Pb with heavy target nuclei at 1 A GeV show indiciations for a simultaneous break-up process. From the average N-over-Z ratio of the final residues up to Z = 70, the average limiting temperature of the break-up configuration at freeze out was determined to T = 5 MeV using the isospin-thermometer method. The phenomenon might be another manifestation of the nuclear liquid-gas-type phase transition. It is consistent with a kind of saturation of the nuclear temperature as a function of excitation energy. In addition, the kinematical properties of the heavy residues carry information on the reaction dynamics.

The Renormalization Group Approach to Neutron Matter
Schwenk, A. (OSU), Friman, B. (GSI), Brown, G.E. (SUNY Stony Brook)
Abstract: We discuss how renormalization group (RG) methods can be applied to the nuclear many-body problem, using an approach proposed by Shankar. The input to these microscopic calculations is the two-body low momentum interaction $V_{\text{low k}}$. $V_{\text{low k}}$ is obtained by integrating out the high momentum components of realistic nucleon-nucleon potentials. It is found that the low momentum $V_{\text{low k}}$ is the same for all studied realistic potential models: Paris, (CD-) Bonn, Argonne, Idaho and the Nijmegen potentials. Moreover, $V_{\text{low k}}$ preserves exactly the accurate reproduction of the experimental phase shifts for laboratory energies $E_{\text{lab}} < 350 \, \text{MeV}$. Starting from $V_{\text{low k}}$, polarization effects due to the many-body medium are included to all orders in the vacuum interaction by solving the RG equation in the particle-hole channels. The resulting quasiparticle interaction includes the induced interaction of Babu and Brown. In addition to the effective interaction, we calculate the in-medium scattering amplitude in the vicinity of the Fermi surface. In the case of back angle scattering, this yields the pairing interaction in infinite matter. Tensor interactions in the medium are included in the RG equations. We present results for the pairing gaps in neutron matter. Finally, we discuss how the RG can be used to derive improved shell model effective interactions for heavy nuclei.

Correlations in 2 and 3 particle decay
Simon, Haik for the FRS-LAND collaboration
Abstract: Nuclear knockout reactions at relativistic energies provide a sensitive tool to determine the ground state properties of nuclei close to the drip line. Studies with kinematically complete measurements allow to reveal the initial correlations in the reacting systems as well as to yield spectroscopic informations on the continuum states populated in the unbound intermediate systems in the decay channel. The coincident data of charged fragments, neutrons and gamma rays allows to unveil as well the possible influence of the reaction mechanism to the interpretation of the measurements. The presently available methods and related observables will be presented together with future perspectives for this type of investigations.

Study of neutron-rich nuclei around the N=40 subshell closure: astrophysical implications
O. Sorlin
Abstract: The structure of nuclei in the vicinity of the N=40 subshell closure has been studied at GANIL via complementary experimental techniques as the Coulomb excitation and the beta-decay. A better understanding of the underlying nuclear structure has been obtained through the determination of B(E2) values, beta-decay half-lives and isomer discoveries. Astrophysical consequences related to the synthesis of neutron-rich stable isotopes as 58Fe, 64Cr, 70Zn from neutron-rich progenitors in a neutron-capture process will be discussed.

Neutron-Rich Rare Isotope Production in Peripheral Reactions around the Fermi Energy
G.A. Souliotis, M. Veselsky and S.J. Yennello (Cyclotron Institute, Texas A\&M University, College Station, Texas, USA)
Abstract: The production of neutron-rich rare isotopes around and below the Fermi energy has been investigated using beams from the K500 Superconducting Cyclotron and the MARS recoil separator at the Cyclotron Institute of Texas A\&M University. Up to date, the reactions of 25 MeV/nucleon $^{86}$Kr + $^{64}$Ni,$^{124}$Sn,$^{112}$Sn and 20 MeV/nucleon $^{124}$Sn + $^{124}$Sn have been investigated for the production of neutron-rich projectile fragments. The experimental results on isotopically resolved cross sections obtained to date will be presented and compared with reaction simulations appropriate for this energy domain. The calculations involve a deep inelastic transfer (DIT) code for the primary interaction stage and a statistical evaporation code (GEMINI) for the de-excitation stage. The results are also compared with higher energy projectile fragmentation data and available parametrizations (EPAX-2). The experimental data on the 25 MeV/nucleon $^{86}$Kr + $^{64}$Ni [1] and also $^{86}$Kr + $^{124}$Sn,$^{112}$Sn, reactions show that both proton-removal and several-neutron pick-up isotopes are produced with large cross sections. We also observe an enhancement in the production of neutron-rich isotopes close to the projectile relative to the predictions of DIT/GEMINI and the expectations of EPAX. We have attributed this enhancement to the effect of the target neutron ``skin'' (especially for the $^{64}$Ni and $^{124}$Sn targets) in the peripheral interactions of $^{86}$Kr with the neutron-rich targets. The experimental data on the 20 MeV/nucleon $^{124}$Sn + $^{124}$Sn for fragments far away from the projectile (Z=20--30), where we mostly focused our attention, show also production of very n-rich nuclides, despite the less peripheral character of these collisions. These nuclides, coming from a larger projectile--target overlap, can be very well described by the DIT/GEMINI simulation. However, as expected for pure projectile fragmentation, EPAX underpredicts the yields of such far-from-projectile neutron-rich products. In general, the large cross sections of neutron-rich nuclides from such reactions around and below the Fermi energy, involving projectile--target nucleon redistribution, suggest that not only the isospin of the projectile and the target, but also their isospin spatial distribution (neutron ``skin'' in the case of $^{64}$Ni and $^{124}$Sn targets) can be properly exploited in the production of neutron-rich rare isotopes. This synthesis approach may offer a fruitful route to extremely neutron-rich nuclei, towards the neutron-drip line, and may be adopted in existing or proposed medium or lower energy radioactive beam facilities. Apart from in-flight possibilities, the option of utilizing this type of reaction for rare isotope production in ISOL-based facilities will be mentioned. Finally, application of such reactions in current plans of both in-flight and IG-ISOL type rare beam production at Texas A\&M will be discussed. \ [1] G.A. Souliotis et al., Phys. Lett. B 543 163 (2002).

Isospin effects in multifragmentation - Review of experiments and interpretations
Trautmann, W. (GSI Darmstadt), A.S. Botvina (GSI Darmstadt, INR Moscow)
Abstract: The majority of isospin effects observed in multifragmentation reactions can be understood within a grandcanonical description of the excited intermediate ensembles formed in the reaction process. This property has successfully been used to follow equilibration processes and to identify emitting sources. Challenging motivations for isospin studies in multifragmentation are derived from the importance of the density dependence of the symmetry term of the equation of state for astrophysical applications and for effects linked to the manifestation of the liquid-gas phase transition in reactions of finite nuclei. Experimental advances aiming at improving our knowledge of the symmetry energy will be presented and discussed.

Alpha Decay Half-Lives of Super-Heavy Nuclei
Typel, S. (GSI), Brown, B. A. (NSCL/MSU)
Abstract: Hartree-Fock calculations with the SKX Skyrme interaction are carried out assuming axial symmetry to obtain alpha-decay Q values of deformed nuclei above $^{208}$Pb. The results for even-even nuclei are compared with experiment and previous calculations. Predictions are made for half-lives of super-heavy nuclei using a global formula.

Short versus long range interactions and the size of
Volpe, C. (INP Orsay and University of Heidelberg)
Abstract: The discovery of halo nuclei and diffuse dimers has generated much excitement both in nuclear and in molecular physics. The relation between the mean square radius and the separation energy (scaling law) in very weakly bound systems can be studied in the context of the two-body problem in quantum mechanics. Using very general arguments, I will discuss the variation of the size of these systems as the energy approaches zero. I will show that, contrary to general belief, not only short range potentials, but also long range ones can give rise to very extended systems, and this for any value of the angular momentum $\ell$. I will argue that, if a natural definition of a halo system arises in the case of short range potentials, this definition is less straightforward for long range potentials. In the case of short range potentials, I will show that scaling laws are strictly independent of the specific shape of the potentials in the case $\ell=0$ only. I will conclude by discussing the applicability of scaling laws to halo nuclei and molecular dimers [1]. [1] R. Lombard and C. Volpe, Phys. Rev. Lett. 88, 190402 (2002).

Studies of reaction dynamics in the Fermi energy domain
M. Veselsky, G.A. Souliotis, S.J. Yennello
Abstract: An overview of recent results on reaction dynamics in the energy region 20 - 50 A.MeV is given. Preliminary results on fragment isospin asymmetry obtained using the 4$\pi$ detector array NIMROD are given. Possibility to extract thermodynamical temperature from systematics of isotope ratios is investigated. Reaction mechanism leading to production of hot sources is discussed. Multifragmentation of the hot source created in violent collisions is investigated using recoil separator MARS where residues from multifragmentation are detected and multifragmentation scenario is determined. Furthermore, the possibilities for production of rare isotopes are discussed and recent experimental results obtained using recoil separator MARS are presented.

Isospin Dynamics in Heavy Ion Reactions
Wolter, H.H., Gaitanos, T. (Univ. of Munich), Di Toro, M, (LNS, Catania)
Abstract: The isovector part of the nuclear equation-of-state is not very well known away from saturation density. It dependence for lower and higher densities as well as the slope at saturation density is very differently predicted by different nuclear structure models. On the other hand this information is important for different phenomena, like the skin thickness of heavy stable nuclei, the neutron skins or halos of exotic nuclei and e.g. also the cooling rate of neutron stars. The density dependence can be investigated at high density in intermediate energy heavy ion collisions in neutron-proton flow differences, and at lower density in nuclear fragmentation, which is seen as a signature of a liquid-gas phase transition. We discuss the low density dependence in this talk. For charge asymmetric systems a qualitative new feature in the liquid-gas phase transition is predicted: the onset of chemical instabilities with a mixture of isoscalar and isovector components. This leads to a separation into a higher density (`liquid') symmetric and a low density (`gas') neutron-rich phase, the so-called neutron distillation effect. We analyse these effects in simulations of heavy ion collisions with respect to the isospin dynamics and to the distribution and asymmetry of the final primary fragments. Qualitatively different effects arise in central collisions with bulk fragmentation and peripheral collisions with neck-fragmentation. The neck fragments produced in this type of process appear systematically more neutron-rich from a dynamical nucleon migration effect which is very sensitive to the symmetry term in regions just below normal density. In general the isospin dynamics plays an important role in all the steps of the reaction, from prompt nucleon emission to the sequential decay of the primary fragments. A fully microscopic description of the reaction dynamics including stochastic elements to treat fluctuations realistically is absolutely necessary in order to extract precise information on the fragmentation and the nuclear equation of state. We have performed such simulations for fragment production events in n-rich (124Sn) and n-poor (112Sn) symmetric colliding systems. We test the dependence of the isospin dynamics on the isospin EOS and on the neutron enrichment of the system. The results seem to indicate an asy-stiff behaviour but the signal is rather weak due to the low initial asymmetry and a washing out in the secondary evaporation.

Novel features of statistical dynamics in a finite system
Shiwei Yan (GSI), Fumihiko Sakata (Ibaraki University), Yizhong Zhuo (China Institute of Atomic Energy)
Abstract: We study features of statistical dynamics in a finite Hamilton system composed of a relevant one-degree of freedom coupled to an irrelevant multi-degree of freedom system through a weak interaction. Special attention is paid on how the statistical dynamics changes depending on the number of degrees of freedom in the irrelevant system. It is found that the macrolevel statistical aspects are strongly related to an appearance of the microlevel chaotic motion, and a dissipation of the relevant motion is realized passing through three distinct stages; dephasing, statistical relaxation, and equilibrium regimes. It is clarified that the dynamical description and the conventional transport approach provide us with almost the same macrolevel and microlevel mechanisms only for the system with a very large number of irrelevant degrees of freedom. It is also shown that the statistical relaxation in the finite system is an anomalous diffusion and the fluctuation effects have a finite correlation time.

Relativistic Hartree theory solved in Woods-Saxon basis
Zhou, S.-G. (Max-Planck-Institut für Kernphysik, Heidelberg, Germany and Peking University, Beijing, China), Meng, J. (Peking University, Beijing, China), Ring, P. (Technische Universität München, Garching, Germany)
Abstract: The relativistic Hartree theory is solved for spherical nuclei in the Woods-Saxon basis obtained by solving either the Sch\"odinger equation or the Dirac equation (labelled as SRHSWS and SRHDWS, respectively and SRHWS for both). When the basis is generated by the Dirac equation, negative levels must be properly included to make the basis complete. We compare in detail the results from SRHWS with those from solving the spherical relativistic Hartree theory in harmonic oscillator basis (SRHHO) and in $r$ space (SRHR). All of these approaches give similar bulk properties, such as total binding energies, radii for both stable and drip line nuclei. However, neutron density distributions of drip line nuclei from SRHHO fall more drastically when $r$ is large, compared to the smoothly decreasing behavior of those from SRHWS and SRHR in the same regime of $r$. Considering the numerical difficulties in solving the mean field theory extended to include deformation and/or pairing in $r$ space for exotic nuclei, the Woods-Saxon basis provides an efficient alternative for the same purpose.