摘要:

In this talk I first present the vacuum for thee+‐e−field of QED and show how it is modified for baryons in nuclear environment. Then I discuss the possibility of producing new types of nuclear systems by implanting an antibaryon into ordinary nuclei. The structure of nuclei containing one antiproton or antilambda is investigated within the framework of a relativistic mean‐field model. Self‐consistent calculations predict an enhanced binding and considerable compression in such systems as compared with normal nuclei. I present arguments that the life time of such nuclei with respect to the antibaryon annihilation might be long enough for their observation. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737091

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Production and decay of an isotope271110 of the 110th element were studied. The isotope was produced by208Pb +64Ni →271110 + n reaction. Fourteen &agr;‐decay chains have been assigned to be the decays originating from the isotope271110. The excitation function of the production cross section was measured. The results have provided a good confirmation of production and decay of the271110 reported by GSI group. The presence of an isomeric state in271110 has also been confirmed. Possible isomeric state in267Hs has also been presented. The production and decay of272111 has been also investigated in irradiations of209Bi targets with64Ni beam. We have observed 14 &agr;‐decay chains in total, that can be assigned, on the basis of their time correlations, to subsequent decays from272111. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737092

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The nuclear shell model predicts that the next doubly magic shell‐closure beyond208Pb is at a proton number Z = 114, 120, or 126 and at a neutron number N = 172 or 184. The outstanding aim of experimental investigations is the exploration of this region of spherical ‘Super‐Heavy Elements’ (SHEs). The measured decay data reveal that for the heaviest elements, the dominant decay mode is &agr; emission, not fission. Decay properties as well as reaction cross‐sections are compared with results of theoretical investigations. Finally, plans are presented for the further development of the experimental set‐up and the application of new techniques. At a higher sensitivity, the exploration of the region of spherical SHEs now becomes feasible, almost forty years after its prediction. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737093

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The paper is focused on reaction dynamics of super‐heavy nucleus formation and decay at beam energies near the Coulomb barrier. The aim is to review the things we have learned from recent experiments on fusion‐fission reactions leading to the formation of compound nuclei withZ⩾ 102 and from their extensive theoretical analysis. Main attention is paid to the dynamics of formation of very heavy compound nuclei taking place in strong competition with the process of fast fission (quasi‐fission). The choice of collective degrees of freedom playing a principal role, finding the multi‐dimensional driving potential and the corresponding dynamic equation regulating the whole process are discussed. Theoretical predictions are made for synthesis of SH nuclei up to Z=120 in the asymmetric “hot” fusion reactions basing on use of the heavy transactinide targets. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737094

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The paper concentrates on one property of superheavy nuclei: height of static spontaneous‐fission barrier. Results of recent macroscopic‐microscopic calculations of this quantity, when axial symmetry of a nucleus is assumed, are illustrated. Effect of non‐axiality of a nucleus on it is discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737095

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We calculate in a macroscopic‐microscopic model fission‐fusion potential‐energy surfaces relevant to the analysis of heavy‐ion reactions employed to form heavy‐element evaporation residues. We study these multidimensional potential‐energy surfaces both inside and outside the touching point.Inside the point of contact we define the potential on a multi‐million‐point grid in 5D deformation space where elongation, merging projectile and target spheroidal shapes, neck radius and projectile/target mass asymmetry are independent shape variables. The same deformation space and the corresponding potential‐energy surface also describe the shape evolution from the nuclear ground‐state to separating fragments in fission, and the fast‐fission trajectories in incomplete fusion.For separated nuclei we study the macroscopic‐microscopic potential energy, that is the “collision surface” between a spheroidally deformed target and a spheroidally deformed projectile as a function of three coordinates which are: the relative location of the projectile center‐of‐mass with respect to the target center‐of‐mass and the spheroidal deformations of the target and the projectile. We limit our study to the most favorable relative positions of target and projectile, namely that the symmetry axes of the target and projectile are collinear. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737096

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Some nuclear mass formulas are reviewed and applied for the heavy and superheavy nuclei. A new mass formula composed of the gross term, the even‐odd term, and the shell term is also presented. The new mass formula is a revised version of the spherical basis mass formula published in 2000, that is, the even‐odd term is treated more carefully, and a considerable improvement is brought about. The root‐mean‐square deviation of the new formula from experimental masses is 641 keV forZ⩾ 8 andN⩾ 8. Properties on systematics of the neutron‐separation energies, alpha‐deacy Q‐values in the superheavy nuclidic region, and Q‐values of the fusion reaction for the heavy nuclei are compared with some mass formulas. Furthermore, a method of estimation for fission half‐lives for the superheavy and neutron‐rich nuclei is presented. With this estimation, the chart of nuclides for the nuclear decays are drawn, and the prediction of limit of the existence in the nuclidic region is discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737097

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The effect of the nuclear shell structure on the heavy‐ion fusion reaction was investigated for the reaction systems82Se +138Ba,82Se +134Ba,16O +204Pb,86Kr +134Ba,86Kr +138Ba, and82Se +nat.Ce. Evaporation residues for these fusion reactions were measured using a recoil mass separator (JAERI‐RMS) near Coulomb barrier region. The measured evaporation residue cross sections for the reactions82Se +138Ba and86Kr +138Ba were two orders of magnitude and one order of magnitude larger than those for the reaction82Se +134Ba and86Kr +134Ba, respectively, at the excitation energy region of 10 ∼ 30 MeV. The evaporation residue cross sections were compared with those of the other reaction systems that make the same or similar compound nuclei as the present reaction systems. It was found that the evaporation residue cross sections correlate strongly with the sum of the shell energies for both projectile and target nuclei, i.e., the evaporation residue cross sections increase as the sum of the shell energy decreases. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737098

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We perform exact coupled‐channels calculations, taking into account properly the effects of Coulomb coupling and the finite excitation energy of collective excitations in the colliding nuclei, for three Fm formation reactions,37Cl +209Bi,45Sc +197Au, and59Co +181Ta. For the37Cl +209Bi and45Sc +197Au reactions, those calculations well reproduce the experimental total fission cross sections, and a part of the extra‐push phenomena can be explained in terms of the Coulomb excitations to multi‐phonon states. On the other hand, for the heaviest system, the deep‐inelastic collisions become much more significant, and the fission cross sections are strongly overestimated. We also discuss the surprisingly large surface diffuseness parameters required to fit recent high‐precision fusion data for medium‐heavy systems, in connection with the fusion supression observed in massive systems. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737099

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The semi‐microscopic potential between heavy nuclei is evaluated for various colliding ions in the approach of frozen densities in the framework of the extended Thomas‐Fermi approximation with ℏ2correction terms in the kinetic energy density functional. The proton and neutron densities of each nucleus are obtained in the Hartree‐Fock‐BCS approximation with SkM*parameter set of the Skyrme force. A simple expression for the nuclear interaction potential between spherical nuclei is presented. It is shown that muon bound with light projectile induces the superheavy elements production in nucleus‐nucleus collisions. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737100

出版商:AIP    

年代:1904

数据来源: AIP