摘要:

Extensive new mass measurement capabilities have evolved with the development of recoil spectrometers. In theZ=3–9 neutron‐rich region alone, 12 direct mass measurements have been determined for the first time by the fast–recoil direct mass measurement method. A recent experiment using the TOFI spectrometer illustrates this technique. A systematic investigation of nuclei that lie along or near the neutron‐drip line has provided a valuable first glimpse into the nuclear structure of such nuclei. No evidence for a large single‐particle energy gap at N=14 is observed; however, a change in the two‐neutron separation energy trend is found at N=15. This change is correctly predicted by shell model calculations, and is interpreted in terms of the smaller 1s1/2–1s1/2interaction compared to that of the Od5/2–Od5/2neutron–neutron interaction.

ISSN:0094-243X    

DOI:10.1063/1.37032

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Mass‐measurements of neutron‐rich nuclei (z= 4 to 15) far from stability have been made at GANIL with the high resolution spectrograph SPEG and time of flight methods. These result are compared to theoretical data. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.37030

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A mass spectrometer has been set up at the on‐line isotope separator ISOLDE at CERN/Geneva. Mass‐separated radioactive ions are stored in a Penning trap. Their mass is determined by a measurement of the cyclotron frequency in the magnetic field of a superconducting magnet. A resolving power of up to 300.000 and a precision of some 10keVwere determined in case of mass measurements of neutron‐deficientRBandCsisotopes. The resonance of the isobars88Srand88Rbwere clearly resolved and evidence was obtained for an isomer in122Cs.

ISSN:0094-243X    

DOI:10.1063/1.37038

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A systematic study of the beta‐decay energies of very neutron‐rich fission products in the mass regions 85≤A≤109 and 130≤A≤150 has been performed in recent years at the mass separators LOHENGRIN and OSTIS at Grenoble, France. From the experimental values of these decay energies—or of binding energies derived from them—it is possible to investigate systematics of nuclear structure effects as a function of mass number A, proton number Z or neutron number N. Several such effects have been observed in the mass regions around A=100 and A=145, namely subshell closures at Z=40 (38) and N=56, and deformations for nuclei with plots of the two‐neutron and two‐proton separation energies calculated from the Q&bgr;‐values measured.

ISSN:0094-243X    

DOI:10.1063/1.36995

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Two weak &agr; groups have been observed in127I‐induced reactions on40Ca. The energies, apparent half‐lives and excitation functions of these &agr; groups have been measured. We confirm and make unambiguous a previous tentative assignment of these &agr; groups to162,163Ta. Our assignment is based on their measured half‐lives as well as on the good agreement between their excitation functions and those exhibited by well‐known &ggr; rays from the decays of162,163Ta, identified in earlier studies with isotope‐separated samples. The mass excesses of162,163Ta, as well as those of seven other nuclides in their &agr;‐decay chains, have been deduced from the &agr;‐decay data obtained in the present work and in previously published studies. The three heaviest members of the163Ta chain are shown to have proton separation energies that are less than zero.

ISSN:0094-243X    

DOI:10.1063/1.37011

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Detection of the &bgr;–decay of fission fragments produced from 600 MeV proton induced fission of a uranium carbide target has been used to measure the mass excess of49,50K and40,42Cl. The experimental data is presented. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.37057

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A project to perform a comprehensive update of the atomic mass predictions has recently been concluded and will be published shortly inAtomic DataandNuclear Data Tables. The project evolved from an ongoing comparison between available mass predictions and reports of newly measured masses of isotopes throughout the mass surface. These comparisons have highlighted a variety of features in current mass models which are responsible for predictions that diverge from masses determined experimentally. The need for a comprehensive update of the atomic mass predictions was therefore apparent and the project was organized and began at the last mass conference (AMCO‐VII). Project participants included: Pape and Anthony; Dussel, Caurier and Zuker; Mo¨ller and Nix; Mo¨ller, Myers, Swiatecki and Treiner; Comay, Kelson, and Zidon; Satpathy and Nayak; Tachibana, Uno, Yamada and Yamada; Spanier and Johansson; Ja¨necke and Masson; and Wapstra, Audi and Hoekstra. An overview of the new atomic mass predictions may be obtained by written request.

ISSN:0094-243X    

DOI:10.1063/1.36976

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The Garvey‐Kelson mass relation has been extended by introducing inhomogeneous source terms to improve problems with long‐range extrapolations. Such mass relations are third‐order partial difference equations with solutions representing mass equations. It was found that inhomogeneous source terms based on shell‐dependent Coulomb and symmetry energy terms are not sufficient to improve upon extrapolations. However, contributions from higher‐order perturbations in isospin (mostly cubic) have a significant effect. A many‐parameter mass equation was constructed as the solution of an inhomogeneous difference equation with properly adjusted shell‐dependent source terms. The standard deviation for reproducing the experimental mass values is &sgr;m=194 keV. Nuclear contributions were subjected to the constraint of charge symmetry, and Coulomb displacement energies are reproduced with &sgr;c=41 keV. Mass predictions for over 4000 nuclei with A≳16 and both N≥Z and N<Z (except N=Z=odd for A<40) are reported.

ISSN:0094-243X    

DOI:10.1063/1.36988

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have developed an approach to the mass formula based on the extended Thomas‐Fermi method with shell corrections calculated by a variant of the Strutinsky method. For extrapolation from known nuclei to unknown nuclei close to the neutron‐drip line this method is essentially equivalent to the Hartree–Fock method, for a given form of force, but is so much faster that the construction of a complete mass table becomes feasible. Preliminary partial fits to the data (491 spherical and 25 deformed nuclei) give rms errors significantly small than is the case with mass formulas based on the droplet model.

ISSN:0094-243X    

DOI:10.1063/1.36941

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The ground‐state energy of an atomic nucleus with asymmetry &bgr; is considered to be equivalent to the energy of a perfect sphere made up of the infinite nuclear matter of the same asymmetry plus a residual energy &eegr; called the local energy. &eegr; represents the energy due to shell, deformation diffuseness and exchange Coulomb effect etc. Using this picture and the generalised Hugenholtz‐Van Hove theorem of many‐body theory a new mass formula has been developed.

ISSN:0094-243X    

DOI:10.1063/1.36956

出版商:AIP    

年代:1987

数据来源: AIP