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From June 17-19 1998 the small, historic English town of Lewes in Sussex bustled with approximately 110 international scientists attending a conference entitled `Nuclear Structure at the Extremes' in the Town Hall. Although the conference was primarily concerned with current and future developments in the field, the subtext was the 40th anniversary of the introduction by J P Elliott of the SU(3) symmetry, which helped to break down the apparent conflict between the nuclear shell model and the collective model. The papers which follow were presented at that conference, except for the first one, entitled `Recollections'. This was provided at the request of many of the participants who wanted to know more about how SU(3) came to be applied to nuclear physics.

The conference was opened by Akito Arima (RIKEN) who gave an overview of the SU(3) model and its development in nuclear physics, and the speakers that followed moved on to a good balance of both experimental and theoretical talks on current topics. Experimental talks included several on techniques, results and prospects for the use of radioactive beams. Other talks included proton scattering from unstable nuclei, magnetic rotation and exotic decays at the proton drip-line. The latest situation on the production of the heaviest elements was also described. Theoretical talks covered the latest Monte Carlo techniques for large-scale shell-model calculations, some very detailed shell-model descriptions of collective phenomena and some formal work on the relation between macroscopic and microscopic models of nuclei. The increasing interest in relativistic descriptions of the nuclear mean-field and its connection with the empirical pseudo-spin symmetry was reflected in several papers. The use in molecular physics of some algebraic techniques developed in nuclear theory was also described.

This conference could not have taken place without the dynamism and enthusiasm of the young scientists involved. Every generation or so, it seems that groups of scientists think that their field is coming to a close, and begin to present it in an historical sense. The movers of this conference were determined to remind others that many new vistas in nuclear structure are just opening, and although still in the emerging stages, they are exciting extensions of solid foundation work already carried out by an older generation. Thus, the talks at this conference were chosen so as to attempt to give an evolutionary context, with the emerging topics as the focus within it.

One further characteristic of this conference came about from a conscious attempt by the organisers to ensure that any artificial divide between experimental and theoretical papers was discouraged; in all talks it was requested that the physics was the focus rather than specialised techniques. This approach seems to have been quite successful in that almost all participants attended almost all of the talks - a noteworthy achievement. One of the senior scientists who attended offered the following comments afterwards: <BLOCKQUOTE> `I thought you might like to know that I thought the event was a resounding success. It was a most pleasant and profitable occasion. Everyone was very friendly and relaxed and the talks were almost universally excellent ... I was wondering in fact what the secret of the meeting might be, because most meetings do not work nearly as well. Apart from the location, which was quite delightful, I think perhaps the fact that speakers were asked to look back as well as forward, gave all the talks a reason to focus on what people already know and then lead them into new concepts. In any event, in spite of a full programme, it was not at all heavy and it was easy to give one's full attention to the talks almost all the time. I don't recall ever being able to do that to the same extent before.' </BLOCKQUOTE>

This conference was supported and sponsored by the University of Brighton. The Institute of Physics contributed five student bursaries.

M K Harder and A M Bruce (Editors) Local Organising Committee M K Harder University of Brighton A M Bruce University of Brighton D D Warner CCLRC, Daresbury P Van Isacker GANIL J P Elliott University of Sussex P H Regan University of Surrey W Gelletly University of Surrey W D Hamilton University of Sussex

Some recollections of the circumstances surrounding the introduction of the group SU(3) into nuclear theory in the late 1950s are reported.

The SU(3) group, its role in bridging the shell model and the collective model, SU(3)-based truncated shell model calculations and puzzles associated with quadrupole-quadrupole interaction together with solutions are briefly described. An overview of various important developments resulting from the application of SU(3) symmetry, and its potential in exploring new frontiers of nuclear structure physics is presented.

The SU3 model of Elliott provides the basic elements that make it possible to understand the collective rotations of nuclei in a spherical shell-model framework. Recent experimental results in medium mass nuclei have delineated new regions of deformation, in places where very large shell-model calculations are now feasible. It turns out that many features of these deformed nuclei can also be understood within an approximate version of SU3.

Recent results on the high-spin states of a range of mid- shell nuclei are presented. Coulomb energy differences (CEDs) as a function of spin have been deduced for the mirror pairs and . A quantitative understanding of the variation of the observed CEDs at high spin is presented in terms of rotational alignment and band-termination effects and we show how the shape-change of the nucleus affects the CED. The experimental results for the CEDs are in excellent agreement with the predictions of a full pf-shell model.

The Elliott SU(3) model, extended via pseudo-spin for heavy nuclei, is used to study low-lying magnetic dipole excitations in deformed nuclei. Proton and neutron degrees of freedom are handled explicitly and the system Hamiltonian includes single-particle energies as well as quadrupole-quadrupole and pairing two-body interactions. The calculated excitation spectra and M1 strength distribution of the strongly deformed even-even Gd isotopes are shown to be in good agreement with experimental results. Results for the -unstable (soft rotor) nucleus and the even-odd system are also reported and found to compare favourably with the available experimental data, demonstrating the ability of the model to describe very different types of systems.

The magnetic behaviour of rotational bands based on natural parity single-quasi-particle states in heavy, deformed nuclei is compared with particle-rotor calculations employing the pseudo-Nilsson scheme. A comparison is also made between the intrinsic magnetic parameters, and , in the Nilsson and pseudo-Nilsson models. For M1 properties, the pseudo-Nilsson approximation is most appropriately applied to high-K orbits and to orbits that occur high in the shell of interest.

We show that pseudo-spin symmetry originates from an SU(2) symmetry of the Dirac Hamiltonian. Furthermore, we demonstrate that pseudo-spin symmetry is approximately conserved for a Dirac Hamiltonian with realistic scalar and vector potentials. We discuss pseudo-SU(3) symmetry in this context as well.

Effective Hamiltonians used for nuclear structure calculations are reviewed. The application of fundamental interactions derived from the nucleon-nucleon scattering data to few-body systems and nuclear matter is reviewed. The special problems in defining the effective Hamiltonian for the nuclear shell-model truncation are discussed. Applications of the Skyrme Hartree-Fock (HF) method are presented, and a method for combining HF and shell-model configuration mixing calculations is discussed.

In experiments at GANIL and GSI, we explored the proton drip line to search for new isotopes and to study the decay modes of nuclei close to the drip line. The study of -delayed proton emission of revealed a very nice agreement between theory and experiment. Studies at GSI enabled us to observe the new isotopes , , and , the latter one being the neighbouring isotope of the doubly-magic nucleus . Finally, at GANIL, the fragmentation of showed clear evidence for the new isotopes , , and . In addition, we performed half-life measurements on and nuclei in this mass region.

The longstanding goal of expressing the nuclear rotor model as a submodel of the shell model is achieved by the use of dynamical groups and spectrum generating algebras. One obtains rotational states as eigenstates of a rotationally invariant Hamiltonian with microscopic shell-model wavefunctions.

Relativistic mean-field theory has also shown great success for the description of nuclear structure at low energies, where relativistic kinematics is not needed. Several phenomena in low-energy nuclear structure are discussed which indicate the relativistic dynamics in nuclei, such as a relativistic saturation mechanisms, the spin-orbit splitting and its isospin dependence, pseudo-spin symmetry as a relativistic theory and nuclear magnetism in rotating nuclei.

Algebraic techniques orginally used in nuclear physics can be extended to molecular systems by combining Lie-algebraic and point-group techniques. The symmetry adaptation gives rise to a direct connection between the algebraic and traditional configuration-space descriptions. We illustrate the model with an application to .

The role of dynamic symmetries in nuclei is briefly reviewed.

The applicability of the generalized BCS approximation in the presence of proton-neutron pairing is studied in the context of two algebraic models. The analysis suggests that approximations based solely on pair correlations cannot describe the ground states of these models. Full symmetry restoration or inclusion of four-body -like correlations is required.

As an alternative to the usual OAI mapping, based on seniority, we investigate the possibility of direct mappings from shell-model SU(3) states to SU(3) states in the IBM.

An extension of the interacting boson model (IBM) is suggested to treat both particle-hole and regular excitations on an equal footing. Particle and hole bosons are introduced, each corresponding to a unitary U(6) algebra. Reduction of the corresponding product algebra leads to the definition of intruder-spin (I-spin). Embedding of the latter into a larger dynamical algebra U(12) gives rise to multiplets that connect states in different nuclei with the same I-spin. Similarly, embedding into a non-compact algebra leads to the classification of multi-particle-multi-hole excitations within one nucleus.

The connection between competing LS and jj coupling schemes and competing T = 0 and T = 1 correlated pairs is recalled and discussed in the light of a shell-model pseudo-SU(4) symmetry which follows from the combined invariance in pseudo-spin and isospin.

The excited states of the self-conjugate, odd-odd system, Ga have been investigated following the fusion-evaporation reaction at a beam energy of 65 MeV. Identification of candidate transitions in this nucleus were made using the AYEBALL -ray array following the selection of the recoil products with the Argonne fragment mass analyser (FMA) and a split anode ionization chamber. Spin assignments have been made on the basis of measured directional correlations from oriented states (DCO ratios). The resulting level scheme is presented and candidates for T = 1 and T = 0 structures suggested.

Recent studies of vibrational excitations in deformed nuclei have led to a close re-investigation of low-lying excitations in deformed nuclei. We have measured lifetimes of levels in three bands at 1199, 1434 and 1772 keV. The results point to the observation of a collective band at 1772 keV that decays to the band at 1199 keV with collective transitions of 5-10 W.u.

In recent work, candidates for two-phonon octupole excitations in have been identified based on the observation of a cascade of E3 decays and on the rates of de-exciting E1 transitions. To gain greater understanding of E1 transition rates in this region, , a nucleus with a neutron hole coupled to the octupole vibrational core of , has been examined. The status of the search for the two-phonon octupole quartet in is presented, and outstanding questions are highlighted.

Lifetimes of states in `rotational-like' M1 bands known in the and regions have been determined through a series of experiments performed with the Gammasphere array. The deduced B(M1) values display a characteristic decrease with increasing angular momentum. This is a clear signature of the `shears' mechanism in which the states in the band are formed from the recoupling of valence proton and neutron spin vectors, and . The rotational-like behaviour of the bands can be interpreted in terms of an effective interaction between and . It has been suggested that the structures are examples of a novel mode of nuclear excitation - `magnetic rotation'.

We propose a quantum Monte Carlo diagonalization method (QMCD) for solving the quantum many-body interacting systems. Not only the ground state but also low-lying excited states are obtained with their wavefunctions. Consequently the level structure of low-lying states can be studied with realistic interactions. The developments in the formulation of the QMCD are described with an illustrative and intuitive example. The QMCD is finally characterized as a `importance truncation' scheme to the shell model. After testing this method for Cr, we present first results for energy levels and E2 properties of Ge, indicating its large and -soft deformation. The doubly closed shell probability of Ni is shown to be only 49% in a full pf shell calculation, in contrast to the corresponding probability of Ca which reaches 86%. The prolate deformed excited band is obtained as a result of the QMCD calculation for non-yrast states, in a good agreement to recent experimental data. This band seems to have an SU(3) (-like) structure which was originally suggested by Elliott for sd-shell nuclei.

After a brief historical review on the naming and discoveries of the trans-fermium elements, recent experimental results are discussed and compared with theoretical predictions. Prospects with current intensity upgrades, radioactive beams and new experimental possibilities such as 4-arrays and traps will be touched upon.

Examples of recent experiments with radioactive beams at intermediate beam energies are given. The neutron halos encountered near the drip line are of an extreme single-particle nature, loosely bound and spatially extended. They are characterized by large electric-dipole strength at low energies that essentially exhausts the relevant cluster sum rules. Other characteristic features are the breakup by shake-off and diffraction dissociation, and the narrow momentum distributions observed for the projectile residue. Finally, some preliminary results on the spectroscopy of single-particle halo and core states by stripping reactions are reported.

We estimate the magnitudes of core excited state cross sections, following halo nucleus dissociation on a light target. Calculations of integrated partial cross sections for the ) reaction at 60 MeV/nucleon are presented and some sensitivities to inputs discussed. Reasonable agreement is obtained with preliminary experimental estimates for this system.

Proton scattering on unstable nuclei is discussed in the light of recent results obtained for and . The macroscopic and microscopic analyses of the data are presented.

The advent of radioactive beams has sparked interest in the structure of exotic nuclei - especially those with extreme neutron excesses. The presence of a neutron skin consisting of a low-density diffuse distribution of nearly pure neutron matter is expected to alter the single-particle structure, residual interactions, and collective modes of these nuclei. Some of these ideas are described along with a discussion of possible signatures of such new phenomena.

We have performed the Be reaction in inverse kinematics. The were detected in the SPEG spectrometer and the deuterons detected in a silicon array in coincidence. The yield to the first excited state of is greater than that to the ground state, and increases with angle. Strong population of the two-alpha plus two-neutron states near 6 MeV (in the two-centre shell-model description) is observed. The ultimate goal is to study the microscopic structure of from the extracted spectroscopic factors.

The heavy odd-odd nuclei , , , have been produced at GANIL by fragmentation of a beam on a natural nickel target. The species of interest were selected and identified by their energy loss in a silicon detector and their time of flight through the LISE spectrometer. The ions were implanted in a silicon strip detector in which their -decay was observed. The measured half-lives for , , correspond to superallowed transitions and may sign Fermi transitions on the basis of values. Our experimental results pave the way for further and more precise measurements of these nuclei.

A highly-deformed, excited band has recently been observed in in an experiment using GAMMASPHERE with the MICROBALL, and a rather analogous band has been found in the isotone using the Pitt-FSU array. They apear to be somewhat intermediate between normal and superdeformed bands and represent the deformation-driving effects of the intruder orbital.

The quadrupole interaction frequency of the high-K five-quasiparticle isomer in implanted in a Tl host at a temperature of 473 K has been determined using the LEMS method. A value of 65.7(7.5) MHz has been found.

Excited states in populated in the -decay of have been identified through -particle-conversion electron coincidences. The level scheme has been interpreted using a configuration mixing calculation, providing estimates of the mixing matrix elements, mixing amplitudes and the energies of unperturbed and unobserved levels.

Microscopic aspects of the Mo-Ba fission channels of are studied using the U(3) selection rule. Effective U(3) symmetry labels, which are consistent with deformation, were used to characterize the parent and daughter nuclei. Our study shows a non-uniform structural dependence of the relative preference for different fission channels.

The low-lying spectrum for is described using the Otsuka, Arima and Iachello mapped interacting boson-fermion model Hamiltonian.

Electron scattering form factors for transitions to low-lying states of are calculated in the symplectic shell model. The significance of multi-shell correlations is discussed.

The projected shell model (PSM) provides a shell model treatment of heavy nuclei, through diagonalization of a pairing plus quadrupole Hamiltonian in an angular momentum projected zero-, two-, and four-quasiparticle basis (for even-even systems). Calculated energy levels and electromagnetic transition amplitudes are in good agreement with the experimental data. Taking as an example, we exhibit the effect of changing the residual interaction strengths on the spectra. It is clearly seen that there are many bandheads whose energies can only be reproduced using the self-consistent strengths. It is concluded that there are no free parameters in the PSM.

We discuss characteristic features of SU(3) partial dynamical symmetry in relation to nuclear spectroscopy and compare with previous broken-SU(3) calculations for .

We investigate the effect of the Coriolis coupling and the residual interactions upon the inter-band transition rates for the vibrational bands and the decay of two-quasiparticle high-K isomers.

We estimated the pre-emission probability for the halo neutron from fusion with carbon target at the 11.25 A MeV beam energy by a sharp cut-off approach.

New results concerning shape coexistence, shape transition and neutron-proton pairing correlations manifested by the lowest few states in a chain of nuclei in the A = 70 region based on large-scale nuclear structure calculations are presented.

Two excited superdeformed bands observed in , which have an identical energy relationship with the even-even core, are suggested to be two members of the pseudo-spin doublet .

We have found the root of the pseudo-spin symmetry to the Dirac equation. We found two kinds of conditions for the pseudo-spin approximation both for the case of the spherical potential and for the deformed potential.

We discuss the application of a theory of large-amplitude collective motion to a simple model mimicking the pairing-plus-quadrupole model of nuclear physics.

We investigate the independent quasiparticle (QP) picture for superdeformed nuclei of the mass-190 region, which is expected to lead to additivity in certain physical quantities. Obvious deviations from additivity are found from both projected shell model calculations and experimental data. The cause of the deviation can be decomposed and identified through this model. Our study suggests that the independent QP picture may not be fully appropriate for this mass region.

Negative-parity excitations in the 2.5 MeV region in have been investigated with the reaction. Several of these states exhibit enhanced B(E2) values for decay to the octupole state, indicative of quadrupole-octupole coupled structures. The B(E1) values observed are typically in the range of 1-, irrespective of the final state.

The decay properties of the lowest band in the SU(3) dynamical limit of the interacting boson model exhibit properties which are not compatible with the classical picture of a -vibration. Induced by this doubt, recent experimental work on and shows that the lowest band can be indeed of various origins in different nuclei.

Light-actinide nuclei in the octupole deformed region have been populated using multi-nucleon transfer from Th. The energy level schemes of several thorium isotopes with A = 228-234 have been extended up to and negative parity states have been observed for the first time in Th. A systematic study of the difference in alignment between the positive- and negative-parity bands in thorium nuclei in this mass region shows that Th behave like octupole vibrators, in contrast with Th, which are octupole-deformed in character. An intrinsic electric dipole moment has been measured for the first time in Th. The small value obtained is consistent with the vibrational description of this nucleus.

By using complete fusion reactions and , leading to and compound nuclei, improved -decay characteristics for neutron-deficient isotopes have been obtained. The experiments have been performed at the fragment mass analyzer (Argonne) and at the RITU gas-filled separator (Jyvaskyla). In the l = 0 decay to the excited state in is two times faster than the decay to the ground state. For more precise values of the alpha-decay energy keV and half-life ms were measured. By using correlated -decay chains -branching ratios of 38(9)% and 9.3(8)% were experimentally deduced for the first time for and , respectively. The reduced -width systematics is extended for even Po isotopes, confirming a persistence of the saturation towards the lighter isotopes. Absence of any anomalies in the reduced -widths for the neutron-deficient Pb isotopes is confirmed.

Excited states have been observed for the first time in ^206,208,210Ra and in each case a decay scheme has been established up to I^π = (8⁺). A sudden fall in excitation energy is observed for the 8⁺ state in ²⁰⁶Ra, along with a large increase in the B(E2) value for the 8⁺–6⁺ transition. This may be evidence for mixing with a deformed structure at spin eight.

We discuss an often overlooked property of the interacting boson model in its simplest version. From a pure group theoretical treatment the IBM-1 has five instead of three dynamical symmetries. The origin and consequences of the two additional symmetries are presented.

We discuss the possible implications of the peculiar recurrence relation which we demonstrate to hold for the series of empirical magic numbers. These include the space-wise shell structure of the nucleus in both the proton and neutron distributions which in -stable nuclei overlap completely, predictions of nuclear halos and skins, the new equation of the line of -stability, predictions for the -stable superheavy nuclei, the effects on the concept of nuclear matter, and a variation of the liquid drop model which partly conforms to such a view of the nucleus.

We investigate the Coulomb dissociation of halo nuclei, assuming that the excitation of the projectile is to states in the low-energy continuum. The method used retains all finite-range effects associated with the interactions between the break-up fragments and can use realistic wavefunctions for the halo nuclei. We apply the method to Coulomb break-up of and on heavy targets, at incident energies below 100 MeV/nucleon, for calculations of alpha particle energy distributions and parallel momentum distributions of , respectively. The absolute magnitudes of the energy distributions and the widths of the parallel momentum distributions are sensitive to the assumed structures of the halo nuclei.

An extension of the interacting boson model (IBM) is suggested by introducting both the particle-hole character and the charge character of the bosons as supplementary degrees of freedom. This allows us to consider an SU(4) symmetry. Within this new classification scheme, three applications are worked out.

Some regularities in the production of isotopes with are investigated in reactions induced by beams at on targets , and . A search for using a beam of the neutron-rich has been performed. Evidence for particle instability of was obtained.

In the same experiment, the half lives of the very neutron-rich isotopes and were measured for the first time.

A new effective two-body interaction of the Gogny type (DIP) is presented. While the merits of the currently used parametrizations (D1 and D1S) remain practically untouched, significant improvements are achieved with respect to three of their main deficiencies: (i) the depth of the optical potential agrees with experiments to energies beyond 200 MeV, (ii) sum rules of Landau parameters are better fulfilled and cleaned from instabilities due to the isovector breathing mode at physical values of the density and (iii) a realistic behaviour for the neutron matter equation of state at high densities is achieved.

A shell-model truncation which has been shown to be useful in the region is applied to several nuclei above and below Z = 28. Comparisions of energy levels with known data suggest the truncation will be useful for workers investigating new data in this region. High-spin isomers are predicted in and .

Nuclei in the region are studied with the shell model. Excitation of particles from the shell is found to be dominated by a pair mode. In fact, such core excited states provide the most important components of the ground state.

In the course of the SHIP experiments aimed to synthesize new elements with atomic numbers , improved decay data on elements Z = (103-109) were also obtained. The presentation of recent results is the subject of this paper.

A SU(3) basis is used to study a Hamiltonian with realistic quadrupole-quadrupole and spin-orbit interactions. The ground state band main components are the S = 0 leading irrep and the leading S = 1 irreps in the proton and neutron subspaces. The quadrupole-quadrupole interaction is found to give dominant weights to the `stretched' coupled representations, supporting a strong truncation of the Hilbert space.

Band structure of are investigated through a constrained generator coordinate method based on self-consistent 3-dimensional cranked Hartree-Fock-Bogoliubov approach. A close analysis of properties of the GCM solutions reveals a possible existence of a tilted rotational motion in its yrast states, as well as a sign of an occurrence of multi-band crossing in the nucleus.

Recent work on the description of odd-odd nuclei in the framework of extended supersymmetry is reviewed. Some on-going experimental programmes are presented.

The quadrupole moments for collective structures in the odd proton (Z = 59) , and nuclei have been measured using the Doppler-shift attenuation method. New information is presented on the shape-driving behaviour of the [404] proton and [541] (, ) neutron Nilsson configurations. While the involvement of the former orbital leads to quadrupole deformations that are comparable to those observed for the so-called superdeformed bands in this mass region, the values for structures that include the 1/[541] neutron are found to lie intermediate between those observed for normally deformed and superdeformed bands.

Very high spin (50-) states in transitional , and nuclei have been studied using the GAMMASPHERE and EUROGAM -ray spectrometers. The lowest energy positive-parity bands in are found to evolve smoothly towards an oblate shape in contrast to the sudden change observed in the neighbouring nucleus. In , the decay path of the positive-parity yrast band splits above and favoured multi-particle-hole states are identified in the irregular pattern at and . The yrast structure of is found to remain collective up to and beyond with no sign of an apparent termination.

A binary cluster model reproduces, without ad hoc symmetry assumptions, the and spin sequences of the low-lying bands in actinide nuclei, as well as the corresponding quasi-rotational excitation energies and enhanced E2 transition rates. The calculations yield very similar radial wavefunctions for levels of a given band up to quite high angular momentum, implying a common intrinsic state for each band. The model can then be extended to reproduce further features more usually associated with the deformed rotor picture.

Ever since the pioneering work of Elliott (Elliott J P 1958 London Series A 245 128, 562), quadrupole collectivity in deformed nuclei has been economically described in terms of symmetry. Microscopic symmetry is not present in the deformed intrinsic states of n nucleons in the abnormal-parity single-particle states . However, such states do possess some -symmetry-like properties as shown in this work.

The yrast states of the beta-stable nucleus have been studied using the reaction at a beam energy of 65 MeV. Transitions in this nucleus were identified unambiguously using high-efficiency recoil-gated gamma-ray spectra obtained from the AYEBALL gamma-ray array in conjunction with the Argonne fragment mass analyser coupled to a split anode ionization chamber. The decay scheme is presented and it is hoped that such a study will shed light on the competition between core breaking and population of the neutron intruder orbitals in the generation of high angular momentum states in this region.

Dynamics of nuclear reactions induced by light, loosely bound proton-rich ions (such as nucleus) at energies from the Coulomb barrier up to 50 MeV/nucleon were studied. The semiclassical modification of the impulse approximation was proposed.

It is shown that the deformation effect decreases the pairing gap similar to the Coriolis anti-pairing effect and the temperature effect. We have confirmed this effect by the numerical analysis based on the constrained Hartree-Fock-Bogoliubov calculation and Nilsson-plus Bardeen-Cooper-Schrieffer calculation.

Long-range correlation in nuclear binding energies are compared with empirical relations in particle mass data and common parameters are derived.

Employing the general principles of classification of states, we have found 285 quantum number isomers (QNI), i.e. nuclei for which there are two possible quantum number sets, characterized by the maximal eigenvalue of the group Casimir operator, at the minimal value for the quantum number of the group symmetric representation, allowed by the Pauli principle. 41 of these QNI can be attributed to the non-excited, ground configurations of realistic nuclei. Two examples of QNI: and , have been studied in detail in the framework of the strictly restricted dynamics model (SRDM).

The microscopic model of -particle states based on the Hamiltonian of broken SU(3) symmetry is developed. The basis of these states is built up. General properties of -particle states of and nuclei are reproduced well enough.

The ground state binding energies and rms radii of the isotopes have been calculated in the minimal approximation of the hyperspherical functions method using different nucleon-nucleon (NN) forces. A reasonable description of the ground state binding energies has been obtained with the Volkov force V1 and the NN potential of Baz' et al (1970 JETP Lett. 12 105) after appropriate choice of the strength of the spin-orbit force. However, the radius is underestimated with V1 and overestimated with the Baz' potential. Both potentials predict that the isotopes are unstable with respect to neutron emission.

Within the Dubna-Livermore collaboration a series of experiments were performed. Experiments with the Dubna gas-filled recoil separator have resulted in the discovery of the new nuclides , , , , and . The ground state decay properties established for and revealed an enhancement in their stability against and spontaneous fission-decays by a factor of as compared with that of nuclides with lower Z and N values. A direct test of the theory was the observation of a decrease in stability for nuclides with Z,N beyond the predicted magic numbers. The -particle energy measured for with N = 163 provided evidence that a neutron shell closure indeed exists and is located at N = 162. Concerning the possibility to reach the Z = 114 region with gas-filled separator some improvements were made to suppress fast background particles.

The high spin states in the the A = 61 isobars, and have been investigated using the AYEBALL -ray array at the Argonne National Laboratory, Chicago. Channel selection following a fusion-evaporation reaction was made using the fragment mass analyser in conjunction with a split anode ionization chamber to obtain isotopically pure -ray identification spectra. The decay schemes, together with spins assigned from a directional correlation analysis are presented and compared with previous work on these nuclei.

In this paper we discuss an approach to the ab initio study of ground states of light nuclei using realistic forces. The method constructs trial variational wavefunctions by superimposing state-dependent translationally-invariant pair correlations on a state-independent Jastrow-correlated wavefunction, with very promising results.

We note the origin of the Wigner term in T = 0 and J = 0 nucleon pair correlations. Empirical evidence indicates that its energy is continuous through a shell region, and it persists through the region 82-126. Z = 126 might well be the next spherical proton magic number after Z = 82.

The possibility of phase transitional behaviour in the Sm nuclei is discussed in relation to recent experiments on , in the context of both interacting boson model and geometric collective model calculations.

The role of dynamic symmetries in the study of nuclear -decay and other weak-interaction processes is discussed.