43 research outputs found
Structure of 8B from elastic and inelastic 7Be+p scattering
Motivation: Detailed experimental knowledge of the level structure of light
weakly bound nuclei is necessary to guide the development of new theoretical
approaches that combine nuclear structure with reaction dynamics.
Purpose: The resonant structure of 8B is studied in this work.
Method: Excitation functions for elastic and inelastic 7Be+p scattering were
measured using a 7Be rare isotope beam. Excitation energies ranging between 1.6
and 3.4 MeV were investigated. An R-matrix analysis of the excitation functions
was performed.
Results: New low-lying resonances at 1.9, 2.5, and 3.3 MeV in 8B are reported
with spin-parity assignment 0+, 2+, and 1+, respectively. Comparison to the
Time Dependent Continuum Shell (TDCSM) model and ab initio no-core shell
model/resonating-group method (NCSM/RGM) calculations is performed. This work
is a more detailed analysis of the data first published as a Rapid
Communication. [J.P. Mitchell, et al, Phys. Rev. C 82, 011601(R) (2010)]
Conclusions: Identification of the 0+, 2+, 1+ states that were predicted by
some models at relatively low energy but never observed experimentally is an
important step toward understanding the structure of 8B. Their identification
was aided by having both elastic and inelastic scattering data. Direct
comparison of the cross sections and phase shifts predicted by the TDCSM and ab
initio No Core Shell Model coupled with the resonating group method is of
particular interest and provides a good test for these theoretical approaches.Comment: 15 pages, 19 figures, 3 tables, submitted to PR
Low-lying states in 8B
Excitation functions of elastic and inelastic 7Be+p scattering were measured
in the energy range between 1.6 and 2.8 MeV in the c.m. An R-matrix analysis of
the excitation functions provides strong evidence for new positive parity
states in 8B. A new 2+ state at an excitation energy of 2.55 MeV was observed
and a new 0+ state at 1.9 MeV is tentatively suggested. The R-matrix and Time
Dependent Continuum Shell Model were used in the analysis of the excitation
functions. The new results are compared to the calculations of contemporary
theoretical models.Comment: 6 pages, 5 figures, accepted as Rapid Communication in Phys. Rev.
Probing the single-particle character of rotational states in F using a short-lived isomeric beam
A beam containing a substantial component of both the ,
ns isomeric state of F and its , 109.77-min ground
state has been utilized to study members of the ground-state rotational band in
F through the neutron transfer reaction , in inverse kinematics.
The resulting spectroscopic strengths confirm the single-particle nature of the
13/2 band-terminating state. The agreement between shell-model
calculations, using an interaction constructed within the shell, and our
experimental results reinforces the idea of a single-particle/collective
duality in the descriptions of the structure of atomic nuclei
Orbifold projection in supersymmetric QCD at N_f\leq N_c
Supersymmetric orbifold projection of N=1 SQCD with relatively small number
of flavors (not larger than the number of colors) is considered. The purpose is
to check whether orbifolding commutes with the infrared limit. On the one hand,
one considers the orbifold projection of SQCD and obtains the low-energy
description of the resulting theory. On the other hand, one starts with the
low-energy effective theory of the original SQCD, and only then perfoms
orbifolding. It is shown that at finite N_c the two low-energy theories
obtained in these ways are different. However, in the case of stabilized
run-away vacuum these two theories are shown to coincide in the large N_c
limit. In the case of quantum modified moduli space, topological solitons
carrying baryonic charges are present in the orbifolded low-energy theory.
These solitons may restore the correspondence between the two theories provided
that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde
Measurement of \u3csup\u3e17\u3c/sup\u3eF + p reactions with ANASEN
Reactions involving radioactive nuclei play an important role in stellar explosions, but those reactions involving short-lived nuclei have only limited experimental information available due to currently limited beam intensities. Several facilities are aiming to provide greater access to these unstable isotopes at higher beam intensities, but more efficient and selective techniques and devices are needed to properly study these important reactions. The Array for Nuclear Astrophysics Studies with Exotic Nuclei (ANASEN), a charged particle detector designed by Louisiana State University (LSU) and Florida State University (FSU), was created for this purpose. ANASEN is used to study the reactions important in the αp- and rp- processes with proton-rich exotic nuclei, providing essentially complete solid angle coverage through an array of 40 silicon-strip detectors backed with CsI scintillators, covering an area of roughly 1300 cm2. ANASEN also includes an active gas target/detector in a position-sensitive annular gas proportional counter, which allows direct measurement of (α,p) reactions in inverse kinematics. The first in-beam measurements with a partial implementation of ANASEN were performed at the RESOLUT radioactive beam facility of FSU during the summer of 2011. They included stable beam experiments and measurements of the 17F(p,p) 17F and 17F(p,α)14O reactions which are important to understanding the structure of 18Ne and the 14O(α,p)17F reaction rate. The performance of ANASEN and initial results from the 17F studies will be presented. © Published under licence by IOP Publishing Ltd
High-K isomers in neutron-rich hafnium nuclei at and beyond the stability line
Pulsed 238U and 208Pb beams have been used to populate multi-quasiparticle high-K isomers in neutron-rich
hafnium isotopes at and beyond the line of b-stability, via inelastic excitation and transfer. Spectroscopic
properties and configuration assignments of several new high-K isomers are compared with earlier theoretical
predictions. A striking example of the robustness of the K quantum number is demonstrated by the observed
competition between E1 and E3 decay modes in 180Hf, the heaviest stable isotope of the element
Yrast three-quasiparticle K isomers in neutron-rich 181Hf
New high-K orbitals have been identified in the neutron-rich 181Hf nucleus via one-neutron transfer from a pulsed 238U beam onto a stable 180Hf target. Yrast three-quasiparticle high-K isomers, with half-lives as long as 1.5 ms, have been populated. The decay scheme of 181Hf has been extended to (25/2-). Blocked BCS calculations, including residual interactions, compare well with the experimental results
Inelastic excitation of new high-spin yrast isomers in 180Ta
For the first time, six-quasiparticle isomers have been observed in the meta-stable nucleus 18073Ta107. Two new high-spin isomers were populated following deep-inelastic reactions with a pulsed 23892U beam incident on a thick 18072Hf target. Out-of-beam γ-ray events were collected using the Gammasphere germanium detector array. In addition to the known four-quasiparticle isomers, yrast Kπ = (22-) and K≥23 six-quasiparticle isomers have been observed with microsecond half-lives. These are the highest-spin isomers observed using the technique of deep-inelastic excitation. The assignments are compared to predictions made by BCS and Lipkin-Nogami multiquasiparticle calculations