Complete destruction of heavy nuclei by hadrons and nuclei

The total disintegration is considered of nuclei with atomic weights ～100 and 200 by high energy hadrons and He⁴, C¹² nuclei with a momentum of 4.5 GeV/c per nucleon. It is shown that mainly nucleons are emitted, and there is no residual nucleus the mass of which is comparable to that of the primary nucleus. The probability of total disintegration is considered as a function of projectile energy and mass. The multiplicity, energy and emission angle of particles are considered as well. It is shown that the density of nuclear matter in the overlap zone of colliding nuclei exceeds the usual one by a factor of ～4. A comparison is made with interaction models. A conclusion is drawn of the collective interaction mechanism (perhaps, of the shock wave type) of particle ejection from the target nucleus at the first stage of interaction and of explosive decay of the residual nucleus at the next one.     

Masses of nuclei

The study of masses of the different nuclear species is basic to the whole of nuclear physics. Because of the interchangeability of mass and energy the details of energy absorption or release are identical with mass differences or changes in the masses of participating nuclei. The systematic trends in mass value reflect therefore changes in the nuclear binding energy. It is one of the primary tasks of nuclear theory to explain the total binding energy of a lump of nuclear matter. The systematic trends in mass differences are also of basic importance in evolving models to describe the formation of the elements in our galaxy.     

Peripheral interactions of relativistic 14N nuclei with emulsion nuclei

The results of investigation of the dissociation of the 2.86-A-GeV/c ¹⁴N nucleus in an emulsion are presented. The cross sections for various fragmentation channels are given. The invariant approach to analysis of fragmentation is used. The momentum and correlation characteristics of the α particles for the ¹⁴N → 3α + X channel in the laboratory system and c.m.s. of three α particles are examined. The results obtained for the ¹⁴N nucleus are compared with similar data for the ¹²C and ¹⁶O nuclei.     

Potential of interaction between nuclei and nucleon-density distribution in nuclei

Nuclear-interaction potentials that are calculated by using Skyrme forces within the extended Thomas-Fermi approximation and Hartree-Fock-Bardeen-Cooper-Schrieffer theory are studied in detail. It is shown that the nuclear component of the potential simulating the interaction between nuclei grows with increasing number of neutrons in colliding isotopes and with increasing diffuseness parameter of the density distribution in interacting nuclei. An increase in the diffuseness parameter of the density distribution in interacting nuclei leads to a decrease in the height of the barrier between the nuclei and to an increase in the depth of the capture well and in the fusion cross section. It is shown that the diffuseness parameter calculated for the nuclear component of the potential at large distance between interacting nuclei by using Skyrme forces exceeds the diffuseness parameter of the nucleon-density distribution in these nuclei by a factor of about 1.5. Realistic values of the diffuseness parameter of nuclear interaction between medium-mass and heavy nuclei fall within the range a ≈ 0.75–0.90 fm.     

Dripline nuclei

A review of some recent experimental studies of dripline nuclei is given. The main emphasis is devoted to light nulcei and especially to the occurrence of halo states.     

Bubble nuclei

These are shells in the single-particle spectrum of a bubble nucleus. The shell-corrected deformation energies, calculated with Strutinsky's theory of renormalization, show that ³⁶Ar, ⁸⁴Se, ¹³⁸Ce, ²⁰⁰Hg in their ground or low-lying excited states are bubble nuclei with a small hole in the interior while ¹⁷⁴Yb and ²⁵⁰104 have secondary minima in the bubble degree of freedom.     

Photofission of nuclei with allowance for wriggling vibrations of fissioning nuclei

It is confirmed that one source of the large relative orbital momenta L of fragments in spontaneous and stimulated low-energy nuclear fission is quantum transverse zero-point wriggling vibrations of the fissioning system near its scission point. The angular distributions of fragments of low-energy photofission of actinide nuclei, calculated using the quantum theory of fission, are compared. Vibrations are allowed for by using parameter C _w determined by Nix and Swiatecki. Agreement between the experimental and theoretical angular distributions for ²³⁴U, ²³⁶U, ²³⁸U, ²³⁸Pu, ²⁴⁰Pu, ²⁴²Pu nuclei is observed. The strong sensitivity of the theoretical angular distributions for ²³⁸Pu, ²⁴⁰Pu, ²⁴²Pu nuclei toward the choice of parameters of transient fissioning states at the external and internal fission barriers is demonstrated.     

Inelastic interactions of fast nucleons with nuclei and fission of nuclei

The cross section for the fission of actinide nuclei that is induced by fast neutrons is considered as a fraction of the cross section for inelastic nucleon interaction with nuclei. In turn, inelastic nucleon interaction with a nucleus is treated as scattering on intranuclear nucleons. It is shown that this interaction model describes satisfactorily the cross section for the inelastic interaction of 60- to 2200-MeV nucleons for a broad set of nuclei and that the energy dependence of the cross section for the fission of actinide nuclei that is induced by 400- to 1000–MeV protons replicates the energy dependence of the cross section for inelastic interactions with respective nuclei. From the model used, it follows that the cross sections for proton-nucleus interactions exceed cross sections for respective neutron-nucleus interactions in the energy range extending up to 550 MeV; at higher energies neutron cross sections are larger than proton cross sections.     

Coulomb energy of nuclei

The density functional determining the Coulomb energy of nuclei is calculated to the first order in e ². It is shown that the Coulomb energy includes three terms: the Hartree energy; the Fock energy; and the correlation Coulomb energy (CCE), which contributes considerably to the surface energy, the mass difference between mirror nuclei, and the single-particle spectrum. A CCE-based mechanism of a systematic shift of the single-particle spectrum is proposed. A dominant contribution to the CCE is shown to come from the surface region of nuclei. The CCE effect on the calculated proton drip line is examined, and the maximum charge Z of nuclei near this line is found to decrease by 2 or 3 units. The effect of Coulomb interaction on the effective proton mass is analyzed.     

Fusion of halo nuclei

The sub-barrier fusion of halo nuclei such as ¹¹Be and ¹¹Li with heavy target nuclei is discussed. The couplings to the soft dipole mode as well as to the break-up channels are taken into account. At barrier energies, the fusion cross section was found to be more than one order of magnitude smaller than that corresponding to the uncoupled problem. At sub-barrier energies, it was shown to be larger.     

Reactions of massive nuclei for the synthesis of heavy and superheavy nuclei

We study the effect of the entrance channel and the shell structure of reacting massive nuclei on the fusion mechanism and the formation of evaporation residues of heavy and superheavy nuclei. In the framework of the combined dinuclear system concept and advanced statistical model, we analyze the reactions ³²S+¹⁸²W, ⁴⁸Ti+¹⁶⁶Er and ⁶⁰Ni+¹⁵⁴Sm leading to ²¹⁴Th^*, and the reactions ⁴⁸Ca+²⁴⁸Cm and the ⁴⁸Ca+²⁴⁹Cf leading to the ²⁹⁶116 and ²⁹⁷118 compound nuclei, respectively.     

Binding energies of nuclei

A new theoretical method is proposed to describe known properties of nuclei. The method is based on the theory of nuclear forces given in an earlier paper and results in formulas for the binding energies and dimensions of nuclei which accord with experimental data.     

Polarization of quadrupolar nuclei

A method of obtaining high polarization and pure spin states of impurity nuclei with a moderately strong quadrupole interaction in solid diamagnetic hosts whose nuclei have spin 1/2, a large g factor (like ¹H and ¹⁹F), and a high degree of polarization is proposed. The method employs cross-relaxation transitions of the impurity nuclei with the host spins (with adiabatic variation of the external magnetic field) and simple radio-frequency pulses that invert the host nuclei or give rise to two-spin resonance of the host and impurity nuclei. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 7, 539–543 (10 October 1998)     

Molecular structure of nuclei

Cluster structures of nuclei are discussed, with emphasis on nuclear clustering in unstable nuclei. The subjects we discuss are alpha condensed states, clustering in Be and B isotopes, and clustering in ³²Mg and ³⁰Ne. The subject of alpha cluster condensation comes from the clustering nature of dilute nuclear matter. We discuss that recent heavy-ion central collision experiments give us nice evidence of the clustering in dilute nuclear matter. We then present a new prediction of the existence of the “alpha cluster condensed states” in the self-conjugate 4n nuclei around the breakup threshold energy into n alpha-particles. As for the clustering in neutron-rich Be, we discuss the comparison between the antisymmetrized molecular-dynamics results and the recent experimental data, which shows that the clustering feature manifests itself very clearly in neutron-rich Be isotopes both in the ground and excited states. Clustering in Be isotopes near neutron dripline is intimately related to the breaking of the neutron magic number N = 8. We report our recent study about the possible relationship between the clustering and the breaking of the neutron magic number N = 20 in ³²Mg and ³⁰Ne. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: horiuchi@ruby.scphys.kyoto-u.ac.jp     

Generalized shells in nuclei: Hartree-Fock calculations for bubble nuclei

Hartree-Fock calculations in the bubble degree of freedom have been performed on a variety of spherical nuclei. Of particular importance are incipient bubble configurations in ³⁶Ar, ⁶⁸Se, ⁸⁴Se, ¹⁰⁰Sn, ¹¹⁶Ce, ¹³⁸Ce and ²⁰⁰Hg, each of which possesses a binding energy which is comparable to that of the normal spherical closed-shell configuration. The densities of the above nuclei display strong deviations from a uniform shape, and give rise to depletions in the nuclear interior. These nonuniformities are due both to the absence of low angular momentum states in otherwise normally occupied spherical shells, and also to strong self-consistency effects. The nonuniformities in the mass density are further enhanced for nuclei whose neutron and proton densities have depressions or peaks at approximately the same distance from the center of the nucleus. A depression of the central density is most pronounced in the nuclei ³⁶Ar, ¹³⁸Ce and ²⁰⁰Hg. Interior depletions of the density are associated with the relatively higher energies of low angular momentum single-particle levels as compared to high angular momentum single-particle levels. This effect can give rise to moderately large gaps at the Fermi surface. Finally, it is shown that in a bubble configuration, the spin-orbit splitting of low lying doublets is sometimes reversed, and that this effect is especially pronounced for levels with low angular momentum.     

Pseudorapidity configurations in collisions between gold nuclei and track-emulsion nuclei

A method of parametrically invariant quantities is developed for studying pseudorapidity configurations in nucleus-nucleus collisions involving a large number of secondary particles. In simple models where the spectrum of pseudorapidities depends on three parameters, the shape of the spectrum may differ strongly from the shape of pseudorapidity configurations in individual events. Pseudorapidity configurations in collisions between gold nuclei of energy 10.6 GeV per nucleon and track-emulsion nuclei are contrasted against those in random stars calculated theoretically. An investigation of pseudorapidity configurations in individual events is an efficient method for verifying theoretical models.     

Molecules in nuclei

The possible existence of analogues of atomic molecules within nuclei is considered in the context of the neutron-rich beryllium and carbon isotopes, where the underlying α cluster structure is believed to produce a multi-centred potential in which valence neutrons move. The generation of molecular wave-functions is examined and the link with the deformed harmonic oscillator and the Nilsson single-particle level scheme traced. Experimental evidence for the existence of molecular exotic cluster structures is reviewed particularly the nature of spectroscopic information provided by break-up reaction measurements. To cite this article: M. Freer, C. R. Physique 4 (2003).     

Chaotic fragmentation of nuclei

The reaction mechanisms for intermediate energy heavy ion collisions are discussed. A simple analytical statistical model for multifragmentation of the colliding nuclei is presented.     

Brueckner theory of nuclei

This paper reviews developments of the Brueckner theory of nuclei, starting with the multiple-scattering approach in the 1954 papers of Brueckner et al. Inevitably, the presentation represents the authors personal view on the problems. Theories rather than calculations have been emphasized. The latter depend very much upon the two-nucleon interaction which is still not known in sufficient detail. The definition of the Brueckner reaction-matrix is discussed at some length with regard to insertions in hole- and particle-lines. Löwdin's Exact Self-Consistent-Field theory that provides an exact many-body reaction matrix is given a short presentation for comparison with Brueckner's theory as applied to finite nuclei. Considerable attention has been given to the shell-model potential required for calculations on finite nuclei. The concept of single-particle energies is discussed in some detail in relation to removal energies. Some numerical results are reviewed either for illustrating the theory or because they are recent.