121631668
A high energy-resolution zero degree facility for (p,p′) and (p,t) reactions
Medium-energy hadronic scattering and reactions at zero degrees are very selective to excitations with low angular momentum transfer. Only a few facilities exist worldwide where high energy-resolution measurements of this nature can be performed. The K600 Zero-Degree Facility at iThemba LABS, South Africa, was recently successfully developed. Measurements were performed for inelastic proton scattering at an incident energy of 200 MeV for targets ranging from 27Al to 208Pb. Excitation energy-resolution of 50 keV (FWHM) was achieved. A reasonable background subtraction procedure allows for the extraction of excitation energy spectra with low background. Measurements of the (p,t) reaction at 100 MeV benefit from a large difference in magnetic rigidity between the reaction products and primary particles, resulting in almost background-free spectra with excitation energy-resolution of 32 keV (FWHM).
118470901
Signature inversion in the yrast band of Ta-164
Excited states in Ta-164 were populated in the Nd-142(Al-27,5n)Ta-164 reaction and investigated using the AFRODITE spectrometer Arran. The yrast rotational decay sequence Lip to spin 21(-) is identified for the first time and assigned to the pi[514]9/2(-) x nu[660]1/2(+) configuration. A less intense. excited hand is also identified. Low-spin signature inversion is observed in the yrast band, and is compared with the extended total Routhian surface calculations. It is likely that quadrupole pairing plays a role in generating the anomalous signature splitting, but an additional mechanism apart front the assumed mean field and quadrupole pairing interaction may be required to account for the experimental data.
122046656
Close near-degeneracy in a pair of four-quasiparticle bands in Tl-194
A pair of rotational bands associated with the pi h(9/2) circle times nu i(13/2)(-1) configuration at lower spins and with the pi h(9/2) circle times nu i(13/2)(-3) configuration at higher spins is found in Tl-194. The two 4-quasiparticle bands show exceptionally close near-degeneracy in the excitation energies. Furthermore close similarity is also found in their alignments and B(M1)/B(E2) reduced transition probability ratios. Such close near-degeneracy probably indicates chiral geometry in the angular momentum space. (c) 2013 Elsevier B.V. All rights reserved.
55476809
Evidence for Partial Taylor Relaxation from Changes in Magnetic Geometry and Energy during a Solar Flare
Context. Solar flares are powered by energy stored in the coronal magne tic field, a portion of which is released when the field reconfigures into a lower energy state. Investigation of sun spot magnetic field topology during flare activity is useful t o improve our understanding of flaring processes. Aims. Here we investigate the deviation of the non-linear field con figuration from that of the linear and potential configuratio ns, and study the free energy available leading up to and after a flare . Methods. The evolution of the magnetic field in NOAA region 10953 was ex amined using data from Hinode/SOT-SP, over a period of 12 hours leading up to and after a GOES B1.0 flare. Previous w ork on this region found pre- and post-flare changes in photos pheric vector magnetic field parameters of flux elements outside the primary sunspot. 3D geometry was thus investigated using potential, linear force-free, and non-linear force-free field extrapo lations in order to fully understand the evolution of the fiel d lines. Results. Traced field line geometrical and footpoint orientation di fferences show that the field does not completely relax to a full y potential or linear force-free state after the flare. Magnet ic and free magnetic energies increase significantly ∼ 6.5‐2.5 hours before the flare by ∼ 10 31 erg. After the flare, the non-linear force-free magnetic ene rgy and free magnetic energies decrease but do not return to pre-flare ‘quiet’ values. Conclusions. The post-flare non-linear force-free field configuration is c loser (but not equal) to that of the linear force-free field configuration than a potential one. However, the small degre e of similarity suggests that partial Taylor relaxation has occurred over a time scale of∼ 3‐4 hours.
119683797
Noncommutative Spherically Symmetric Space
We examine some noncommutative spherically symmetric spaces in three space dimensions. A generalization of Snyder’s noncommutative (Euclidean) space allows the inclusion of the generator of dilations into the defining algebra of the coordinate and rotation operators. We then construct a spherically symmetric noncommutative Laplacian on this space having the correct limiting spectrum. This is presented via a creation and annihilation operator realization of the algebra, which may lend itself to a truncation of the Hilbert space.
119293158
Noncommuting coordinates and magnetic monopoles
The appearance of noncommuting spatial coordinates is studied in quantum systems containing a magnetic monopole and under the influence of a radial potential. We derive expressions for the commutators of the coordinates that have been restricted to the lowest energy level. Quantum corrections are found to previous results by Frenkel and Pereira based on quantizing the Dirac brackets of the classical theory. For two different potentials, the modified harmonic oscillator potential and the modified Coulomb potential, we also calculate the commutators for a projection to a fixed energy level.