436 research outputs found
SU(3) quasidynamical symmetry underlying the Alhassid--Whelan arc of regularity
The first example of an empirically manifested quasi dynamical symmetry
trajectory in the interior of the symmetry triangle of the Interacting Boson
Approximation model is identified for large boson numbers. Along this curve,
extending from SU(3) to near the critical line of the first order phase
transition, spectra exhibit nearly the same degeneracies that characterize the
low energy levels of SU(3). This trajectory also lies close to the
Alhassid-Whelan arc of regularity, the unique interior region of regular
behavior connecting the SU(3) and U(5) vertices, thus offering a possible
symmetry-based interpretation of that narrow zone of regularity amidst regions
of more chaotic spectra.Comment: 4 pages, LaTeX, 5 eps figure
Alternative Interpretation of Sharply Rising E0 Strengths in Transitional Regions
It is shown that strong 0+2 -> 0+1 E0 transitions provide a clear signature
of phase transitional behavior in finite nuclei. Calculations using the IBA
show that these transition strengths exhibit a dramatic and robust increase in
spherical-deformed shape transition regions, that this rise matches well the
existing data, that the predictions of these E0 transitions remain large in
deformed nuclei, and that these properties are intrinsic to the way that
collectivity and deformation develop through the phase transitional region in
the model, arising from the specific d-boson coherence in the wave functions,
and that they do not necessarily require the explicit mixing of normal and
intruder configurations from different IBA spaces.Comment: 6 pages, 3 figure
The role of the g9/2 orbital in the development of collectivity in the A = 60 region: The case of 61Co
An extensive study of the level structure of 61Co has been performed
following the complex 26Mg(48Ca, 2a4npg)61Co reaction at beam energies of 275,
290 and 320 MeV using Gammasphere and the Fragment Mass Analyzer (FMA). The
low-spin structure is discussed within the framework of shell-model
calculations using the GXPF1A effective interaction. Two quasi-rotational bands
consisting of stretched-E2 transitions have been established up to spins I =
41/2 and (43/2), and excitation energies of 17 and 20 MeV, respectively. These
are interpreted as signature partners built on a neutron {\nu}(g9/2)2
configuration coupled to a proton {\pi}p3/2 state, based on Cranked Shell Model
(CSM) calculations and comparisons with observations in neighboring nuclei. In
addition, four I = 1 bands were populated to high spin, with the yrast dipole
band interpreted as a possible candidate for the shears mechanism, a process
seldom observed thus far in this mass region
Use of Malaria Rapid Diagnostic Test to Identify Plasmodium knowlesi Infection
Reports of human infection with Plasmodium knowlesi, a monkey malaria, suggest that it and other nonhuman malaria species may be an emerging health problem. We report the use of a rapid test to supplement microscopic analysis in distinguishing the 5 malaria species that infect humans
Anomalous behavior of the first excited 0 state in nuclei
A study of the energies of the first excited states in all even-even
8 nuclei reveals an anomalous behavior in some nuclei with =
, 2. We analyze these irregularities in the framework of the shell
model. It is shown that proton-neutron correlations play an important role in
this phenomenon.Comment: 4 pages, 5 figure
On the lifetime of the 2+ state in 10C
The lifetime of the J=2+ state in 10C was measured using the Doppler Shift
Attenuation Method following the inverse kinematics p(10B,n)10C reaction at 95
MeV. The 2+ state, at 3354 keV, has tau = 219\pm(7)stat \pm(10)sys fs
corresponding to a B(E2) # of 8.8(3) e2fm4. This measurement,combined with that
recently determined for 10Be (9.2(3) e2fm4), provides a unique challenge to
abinitio calculations, testing the structure of these states, including the
isospin symmetry of the wave functions. Quantum Monte Carlo calculations using
realistic two- and three-nucleon Hamiltonians that reproduce the 10Be B(E2)
value generally predict a larger 10C B(E2) probability but with considerable
sensitivity to the admixture of different spatial symmetry components in the
wave functions, and to the three-nucleon potential used.Comment: Experimental and Theoretical Investigatio
- …