[en] The international seminar on nuclear physics with radioactive ion beams and high spin structure organized by the Institute of Modern Physics was held from September 1-4, 1998 in Lanzhou.Some of new results of the studies on high spin structure were presented here.The nuclear masses with high accuracy measured recently by means of ESR at GSI were also reported in this seminar.Some theoretical results and experimental observations on the nuclear physics with radioactive ion beams were also introduced.The topic of the investigations of giant dipole resonance was included in this seminar

[en] High spin states of the proton rich nuclei in the mass region A ≅100 have been studied at the GASP and recently at the EUROBALL γ-ray spectrometers. Of the several nuclei populated in the reactions the authors will discuss here the high spin states of ¹⁰⁵In, ¹⁰⁵Sn and ¹⁰⁹Te as examples for magnetic rotation and octupole collectivity. For ¹⁰⁵In and ¹⁰⁵Sn regular sequences of dipole transitions have been found. The states of the dipole bands are suggested to be built on neutron h_11/2 excitations coupled to proton hole states, which polarize the core to a slightly prolate shape. The experimental results are in agreement with the prediction of tilted axis cranking calculations. For the ¹⁰⁹Te nucleus has been identified two bands of opposite parity connected by strong dipole transitions of E1 character. Octupole correlations induced by rotation are suggested as the cause of this effect

[en] Beams of relativistic exotic nuclei were produced, separated and investigated with the combination of the fragment separator FRS and the storage ring ESR. The following experiments are presented: 1) Direct mass measurements of relativistic nickel and bismuth projectile fragments were performed using Schottky spectrometry. Applying electron cooling, the relative velocity spread of the circulating secondary nuclear beams of low intensity was reduced to below 10^-6. The achieved mass resolving power of m/Δm = 6.5·10⁵ (FWHM) in recent measurements represents an improvement by a factor of two compared to authors' previous experiments. The previously unknown masses of more than 100 proton-rich isotopes have been measured in the range of 54≤Z≤84. The results are compared with mass models and estimated values based on extrapolations of experimental values. 2) Exotic nuclei with half-lives shorter than the time required for electron cooling can be investigated by time-of-flight measurements with the ESR being operated in the isochronous mode. This novel experimental technique has been successfully applied in a first measurement with nickel fragments. A mass resolving power of m/Δm = 1.5·10⁵ (FWHM) was achieved in this mode of operation. 3) Nuclear half-lives of stored and cooled bare projectile fragments have been measured to study the influence of the ionic charge state on the beta-decay probability

[en] Within the framework of an isospin-dependent quantum molecular dynamics model in which the initial neutron and proton densities are sampled according to the densities calculated from the Skyrme-Hartree-Fock method and the initial Fermi momenta of neutron and proton are calculated from the Fermi gas model, the authors study systematically the transverse collective flow of different fragment types at energy of 55 MeV/nucleon and the balance energy in reactions ⁵⁸Fe + ⁵⁸Fe and ⁵⁸Ni + ⁵⁸Ni. The present calculated results indicate that the neutron-rich system (⁵⁸Fe + ⁵⁸Fe) displays stronger negative deflection and has a higher balance energy, which are qualitatively in agreement with the experimental data. Meanwhile, the effects of the isospin-dependent symmetry energy and nucleon-nucleon cross sections on collective flow are also studied

[en] Nuclei ¹⁰⁰Sn, which represents a double shell closure, were investigated at the on-line isotope-separator of GSI. The recent progress with respect to the studies of direct proton emission (¹⁰⁵Sb), direct ¹²C-cluster decay (¹¹⁴Ba), β-delayed γ-ray emission (^107,108Sb, ¹⁰³In, ⁹⁷Ag), and of β-delayed proton decay (^96,98Ag, ⁹⁸Cd) is presented. Emphasis is put on evidence for the Gamow-Teller resonance near ¹⁰⁰Sn

[en] The formalism for Relativistic Continuum Hartree-Bogoliubov (RCHB) theory which is the extension of the Relativistic Mean Field (RMF) and the Bogoliubov transformation in the coordinate representation, and its application to unstable nuclei are reviewed. As the RCHB formalism allows for the proper description of the coupling between the bound state and the continuum by the pairing force, it is suitable not only for stable nuclei but also the nuclei near the drip line. The pairing correlations are taken into account by both a density-dependent force of zero range and the finite range Gogny force. The RCHB theory is suitable to describe the nuclei extending from the proton drip line to the neutron drip line

[en] The study of extremely deformed nuclear is a field of growing interest in nuclear physics. As an example of extremely deformed system, the incomplete fusion reaction ⁶⁴Ni(¹²C,α)⁷²Zn is given. An enhancement of the emitted gamma ray energy spectrum around 10 Mev in the reaction is observed. Such enhancement is the evidence of the excitation of a dynamical dipole in the dinuclear system. This study is at the lower limit of the spin predicted for super deformations; an extension to higher spin and slightly different nuclei would be quite interesting allowing the detection of high energy gamma rays from superdeformed levels

[en] The authors have measured the interaction cross sections (σ₁) and one-neutron removal cross-sections (σ_-n) of ^12-20C at its energies ∼950 A MeV. The authors observed larger σ₁ and σ_-n values for ¹⁹C than for those of neighbors. The authors have deduced the matter density distribution of ¹⁹C that reproduces the observed σ₁. The deduced density exhibits the halo structure of ¹⁹C. Similar analysis applied to ¹¹Be. The presently deduced density for ¹¹Be is well consistent with that previously deduced from the energy dependence of reaction cross-sections. The authors also discussed longitudinal-momentum distributions of ¹⁸C from ¹⁹C breakup

[en] The interplay between collective and non-collective degrees of freedom is well accounted for in configurations evolving from rotational behaviour to terminating sates. These states are characterized by spins built from the angular momentum of the valence holes and valence particles and by oblate (γ = +60 degree) or prolate (γ = -120 degree) shape. Results obtained with the multidetector EUROGAM2 are presented. The cases of ¹⁰²Pd, which is the first nucleus in which terminating bands built on valence space and core excited configurations have been observed, and ¹⁰²Rh, which is the first odd-odd nucleus between the Z = 28 and Z = 50 shell closures in which terminating bands have been found, are discussed. Comments are made on lifetimes and transitions feeding the terminations

[en] Reliable and accurate lifetimes can be deduced using the differential decay-curve method (DDCM) for the analysis of coincidence recoil distance Doppler shift data obtained from large γ ray spectrometers like GASP, EUROBALL or GAMMASPHERE. Lifetimes of excited states in ¹³⁴Nd and ¹³⁰Ba were measured with a high precision using the GASP spectrometer at Legnaro and the 3 x 3 Euroball-Cluster setup at Heidelberg, respectively. In addition lifetimes of excited states in the odd neighbouring nuclei ¹³⁵Nd and ¹²⁹Ba were obtained. The deduced transition probabilities were used for sensitive tests of various collective nuclear models. The B(E2.0⁺→2⁺) values of neutron deficient even even nuclei in the A = 130 mass region are described as a function of the product of valence proton particles and valence neutron holes. Shape effects indicated by increasing B(E2) values in the yrast bands of ¹³⁴Nd and ¹²⁶Ba are discussed. Band mixing calculations were performed to describe energies, branching ratios as well as absolute transition probabilities for the decay out of the SD band in ¹³³Nd and for the band crossing of the ground state band with two S-bands in ¹³⁰Ba