Mass predictions, partial difference equations and higher‐order isospin effects

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 σm=194 keV. Nuclear contributions were subjected to the constraint of charge symmetry, and Coulomb displacement energies are reproduced with σc=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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87305/2/62_1.pd

Study of the (6-Li,d) Reaction at E(Li)=90 MeV

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

The lowest T = 0 states in the odd N = Z nuclei with A &#62; 40

There is indication that the lowest T = 0 and T = 1 states are inverted not only in Cl34 but also in Sc42, V46, Mn50 and Co54. Isomerism in all these nuclei is likely.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32325/1/0000395.pd

Microscopic structure of fundamental excitations in N=Z nuclei

Excitation energies of the $T$=1 states in even-even as well as $T$=0 and $T$=1 states in odd-odd $N$=$Z$ nuclei are calculated within the mean-field approach. It is shown that the underlying structure of these states can be determined in a consistent manner only when both isoscalar and isovector pairing collectivity as well as isospin projection, treated within the iso-cranking approximation, are taken into account. In particular, in odd-odd $N$=$Z$ nuclei, the interplay between quasiparticle excitations (relevant for the case of $T$=0 states) and iso-rotations (relevant for the case of $T$=1 states) explains the near-degeneracy of these fundamental excitations.Comment: 4 pages, 4 figure

Phenomenological and Microscopic Optical-Model Descriptions of 99 MeV 6-Li Scattering

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

Mixed quark-nucleon phase in neutron stars and nuclear symmetry energy

The influence of the nuclear symmetry energy on the formation of a mixed quark-nucleon phase in neutron star cores is studied. We use simple parametrizations of the nuclear matter equation of state, and the bag model for the quark phase. The behavior of nucleon matter isobars, which is responsible for the existence of the mixed phase, is investigated. The role of the nuclear symmetry energy changes with the value of the bag constant B. For lower values of B the properties of the mixed phase do not depend strongly on the symmetry energy. For larger B we find that a critical pressure for the first quark droplets to form is strongly dependent on the nuclear symmetry energy, but the pressure at which last nucleons disappear is independent of it.Comment: 12 pages, 16 figures, Phys. Rev. C in pres

Atomic Charge Exchange Between Fast Singly- and Doubly-Ionized Helium Ions in Targets from Carbon to Bismuth at β = 0.36

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Target structure independent 7Li⃗^7\vec{Li} elastic scattering at low momentum transfers

Analyzing powers and cross sections for the elastic scattering of polarized 7Li by targets of 6Li, 7Li and 12C are shown to depend only on the properties of the projectile for momentum transfers of less than 1.0 fm-1. The result of a detailed analysis of the experimental data within the framework of the coupled channels model with ground state reorientation and transitions to the excited states of the projectile and targets included in the coupling schemes are presented. This work suggests that nuclear properties of weakly-bound nuclei can be tested by elastic scattering experiments, independent of the target used, if data are acquired for momentum transfers less than ~1.0 fm-1.Comment: 9 pages, 4 figures, 1 table, accepted in Phys. Lett.

The Origin of the Wigner Energy

Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinuity at N=Z. This cusp (Wigner energy), reflecting an additional binding in nuclei with neutrons and protons occupying the same shell model orbitals, is usually attributed to neutron-proton pairing correlations. A method is developed to extract the Wigner term from experimental data. Both empirical arguments and shell-model calculations suggest that the Wigner term can be traced back to the isospin T=0 part of nuclear interaction. Our calculations reveal the rather complex mechanism responsible for the nuclear binding around the N=Z line. In particular, we find that the Wigner term cannot be solely explained in terms of correlations between the neutron-proton J=1, T=0 (deuteron-like) pairs.Comment: 10 RevTeX pages, 3 Postscript figures include

Two-proton events in the 17F(p,2p)16O reaction

In a recent experimental study (Gomez del Campo et al, PRL 86, 43 (2001)) of the reaction 17F(p,2p)16O, two-proton events were measured from excitations near a 1-, E*=6.15 MeV state in 18Ne. We calculate by means of R-matrix theory the resonant two-proton production cross section and branching ratios. We conclude that it is unlikely that two-proton production via population of the 1- state is sufficient to explain the observed two-proton events. Alternative sources of such events are discussed.Comment: 4 pages, 4 figures. Resubmission to Physical Review C (first received 6 March 2001