119 research outputs found
Quadrupole Moments of Neutron-Deficient Na
The electric-quadrupole coupling constant of the ground states of the proton
drip line nucleus Na( = 2, = 447.9 ms) and the
neutron-deficient nucleus Na( = 3/2, = 22.49 s)
in a hexagonal ZnO single crystal were precisely measured to be kHz and 939 14 kHz, respectively, using the multi-frequency
-ray detecting nuclear magnetic resonance technique under presence of an
electric-quadrupole interaction. A electric-quadrupole coupling constant of
Na in the ZnO crystal was also measured to be
kHz. The electric-quadrupole moments were extracted as Na) = 10.3
0.8 fm and Na) = 14.0 1.1 fm, using
the electric-coupling constant of Na and the known quadrupole moment of
this nucleus as references. The present results are well explained by
shell-model calculations in the full -shell model space.Comment: Accepted for publication in Physics Letters
Fast switching NMR system for measurements of ground-state quadrupole moments of short-lived nuclei
A beta-ray detecting nuclear quadrupole resonance system has been developed
at NSCL/MSU to measure ground-state electric quadrupole moments of short-lived
nuclei produced as fast rare isotope beams. This system enables quick and
sequential application of multiple transition frequencies over a wide range.
Fast switching between variable capacitors in resonance circuits ensures
sufficient power delivery to the coil in the beta-ray detecting nuclear
magnetic resonance technique. The fast switching technique enhances detection
efficiency of resonance signals and is especially useful when the polarization
and/or production rate of the nucleus of interest are small and when the
nuclear spin is large
Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System
The beta-ray angular correlations for the spin alignments of 8Li and 8B have
been observed in order to test the conserved vector current (CVC) hypothesis.
The alignment correlation terms were combined with the known beta-alpha-angular
correlation terms to determine all the matrix elements contributing to the
correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the
beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2,
deduced from the analog-gamma-decay measurement based on the CVC hypothesis.
However, there was no consistent CVC prediction for the second-forbidden term
associated with the weak vector current. The experimental value for the
second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4
or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.
Sharpening Low-Energy, Standard-Model Tests via Correlation Coefficients in Neutron Beta-Decay
The correlation coefficients a, A, and B in neutron beta-decay are
proportional to the ratio of the axial-vector to vector weak coupling
constants, g_A/g_V, to leading recoil order. With the advent of the next
generation of neutron decay experiments, the recoil-order corrections to these
expressions become experimentally accessible, admitting a plurality of Standard
Model (SM) tests. The measurement of both a and A, e.g., allows one to test the
conserved-vector-current (CVC) hypothesis and to search for second-class
currents (SCC) independently. The anticipated precision of these measurements
suggests that the bounds on CVC violation and SCC from studies of nuclear
beta-decay can be qualitatively bettered. Departures from SM expectations can
be interpreted as evidence for non-V-A currents.Comment: 4 pages, REVTeX, intro. broadened, typos fixed, to appear in PR
Structure effects on the Coulomb dissociation of 8B at relativistic energies
We investigate the Coulomb dissociation of 8B on 208Pb target at the beam
energy of 250 MeV/nucleon, employing the cross sections for the radiative
capture reaction 7Be(p,gamma)8B calculated within the Shell Model Embedded in
the Continuum (SMEC) approach. In contrast to the situation at lower beam
energies, the Coulomb breakup cross sections are found to be sensitive to the
M1 transitions. Comparisons of SMEC and single-particle potential model
predictions show that the Coulomb breakup cross sections at these high energies
are sensitive to the structure model of 8B. Analysis of the preliminary data
taken recently at GSI reveal that E2 multipolarity contributes up to 25 % to
the cross sections even for the relative energies of p - 7Be below 0.25 MeV.Comment: 22 pages, 7 figure
Ground State Electromagnetic Moments of <sup>37</sup>Ca
The hyperfine coupling constants of neutron deficient Ca were deduced from the atomic hyperfine spectrum of the transition in Ca II, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as and fm, respectively. The experimental values agree well with nuclear shell model calculations using the universal sd model-space Hamiltonians versions A and B (USDA/B) in the -model space with a 95\% probability of the canonical nucleon configuration. It is shown that the magnetic moment of Ca requires a larger non--shell component than that of Ca for good agreement with the shell-model calculation, indicating a more robust closed sub-shell structure of Ca at the neutron number = 16 than Ca. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions
Study of the and capture reactions using the shell model embedded in the continuum
We apply the realistic shell model which includes the coupling between
many-particle (quasi-)bound states and the continuum of one-particle scattering
states to the spectroscopy of mirror nuclei: B and Li, as well as to
the description of low energy cross sections (the astrophysical S factors) in
the capture reactions: and .Comment: 36 pages, 10 figure
Beta-delayed proton emission in the 100Sn region
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fragments of interest were identified
and their decay was studied with the NSCL Beta Counting System (BCS) in
conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing,
98Inm and 99In were identified as beta-delayed proton emitters, with branching
ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for
89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9
-1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for
101Sn was deduced with higher precision than previously reported. The impact of
the newly measured bp values on the composition of the type-I X-ray burst ashes
was studied.Comment: 15 pages, 14 Figures, 4 Table
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