35436961
Predicted features of the beta decay of neutron-rich sd-shell nuclei
The Gamow-Teller beta-decay transitions of sd-shell nuclei with five or more excess neutrons are calculated from complete (0d/sub 5/2/, 1s/sub 1/2/, 0d/sub 3/2/)-space shell-model wave functions. These wave functions are obtained from diagonalizations of a model Hamiltonian formulation which reproduces observed energy-level structures throughout the sd shell. The calculations are carried out with both the ''free-nucleon'' normalization for the Gamow-Teller single-nucleon matrix elements and one based on the empirical values obtained for these quantities from a comparison of corresponding theoretical and experimental Gamow-Teller magnitudes near the line of stability. The phase-space factors f which connect the reduced Gamow-Teller strengths to the total half-lives and the individual decay probabilities are calculated both from the energies obtained in the shell-model calculations and, alternatively, from hybrid energy spectra in which available experimental energies are substituted for the corresponding calculated values wherever possible. Comparisons of the beta-decay predictions to existing experimental results are presented and discussed.
35977510
Quadrupole moments of sd-shell nuclei.
Shell-model calculations are presented for electric quadrupole moments of A = 17-39 nuclei. The shell-model wave functions, which span the complete 0d/sub 5/2/-ls/sub 1/2/-0d/sub 3/2/ model space in all instances, are obtained by diagonalizing an sd-shell Hamiltonian which consists of a fixed single-particle energy spectrum and a single set of two-body matrix elements scaled as a function of the mass number A. Results obtained with harmonic oscillator and Saxon-Woods single-particle radial wave functions and matched effective-charge models are presented for ground states of odd-even and doubly odd nuclei and for J/sup ..pi../ = 2/sup +/ first-excited states of doubly even sd-shell nuclei.
121967474
Shell-model calculation for two-neutrino double beta decay of Ca48
The 2{nu}{beta}{beta} decay matrix element of {sup 48}Ca has been studied in a large basis shell-model space. The theoretical and experimental {beta}{sup {minus}} and {beta}{sup +} spectra and their relation to 2{nu}{beta}{beta} are discussed. A new empirical effective interaction is found to give the best agreement to {beta}{sup {minus}} and {beta}{sup +} spectra with the effective Gamow-Teller operator {tilde {sigma}}{ital t}=0.77{sigma}{ital t}. The predicted {ital T}{sub 1/2}=1.9{times}10{sup 19} yr differs by a factor of 2 from the present experimental limit of {ital T}{sub 1/2}{gt}3.6{times}10{sup 19} yr. We also compare the matrix elements obtained at various levels of the truncation in the shell-model space.
34139540
Shape of the beta spectra in the A=14 system.
39136906
Structure of C-16: Testing shell model and ab initio approaches
Excited states in C-16 were populated via the Be-9(N-17,C-16+gamma)X one-proton knockout reaction. The lifetime of the 2(1)(+) state in C-16 was measured using the recoil distance method. The extracted lifetime of tau(+)(21) = 11.4(-0.9)(+0.8)(stat) +/- 0.7(syst(B rho))(-1.5)(+0.0)(syst(feeding)) ps yields a deduced B(E2;2(1)(+) -> 0(1)(+)) = 4.21(-0.26)(+0.34)(stat)(-0.24)(+0.28)(syst(B rho))(-0.00)(+0.64)(syst(feeding)) e(2)fm(4) value in good agreement with a previous measurement. The one-proton knockout cross section is used to extract the proton amplitude of the C-16 2(1)(+) state, which confirms the neutron dominant character of this state. Gamma-ray branching ratios between the 2(2)(+) state and the 2(1)(+) and ground states were also determined. The results are compared with p-sd shell model and no-core shell model (with NN and NN + NNN) calculations. The inclusion of three-body forces are essential in order for the no-core shell model calculations to reproduce the experimental findings on the gamma-ray branching ratios.
39044560
Neutron halos in the Na isotopes.
The neutron and proton density distributions of the Na isotopes out to the proton and neutron drip lines are calculated in the spherical Hartree-Fock model with a wide variety of density-dependent Skyrme interactions. The results are compared to recent experimental data for the interaction cross sections and for the rms radii. We discuss the role of the deformed intruder states and the problems associated with predicting the location of the neutron drip line for this mass region. {copyright} {ital 1996 The American Physical Society.}
118305517
Causal Structures of Dynamic Black Holes
Dynamic space‐times, especially those manifesting horizons, provide useful laboratories for examining how macroscopic quantum behaviors consistently co‐generate gravitational phenomena. For this reason, the behaviors and large‐scale causal structures of spatially coherent dynamic black holes will be explored in this presentation. Geodesic motions on an evaporating black hole will also be presented. Research recently completed with Beth Brown, including her final Penrose diagram for an accreting black hole, will be presented.
118606402
Radial Photon Trajectories Near an Evaporating Black Hole
The radial motion of photons emitted near the horizon of a black hole that evaporates at a steady rate is examined. The space-time of the black hole is generated using non-orthogonal coordinates. It is shown that some photons that are initially drawn towards the singularity can escape falling into the horizon. The behaviors of various outgoing and ingoing photons are clearly demonstrated through the use of a Penrose diagram.