Approaching the “island of inversion”:P34

Abstract

Yrast states in 34 P were investigated using the 18 O( 18 O,pn) reaction at energies of 20, 24, 25, 30, and 44 MeV at Florida State University and at Lawrence Berkeley National Laboratory. The level scheme was expanded, γ-ray angular distributions were measured, and lifetimes were inferred with the Doppler-shift attenuation method by detecting decay protons in coincidence with one or more γ rays. The results provide a clearer picture of the evolution of structure approaching the "Island of Inversion", particularly how the 1 and 2 particle-hole (ph) states fall in energy with increasing neutron number approaching inversion. However, the agreement of the lowest few states with pure sd shell model predictions shows that the level scheme of 34 P is not itself inverted. Rather, the accumulated evidence indicates that the 1-ph states start at 2.3 MeV. A good candidate for the lowest 2-ph state lies at 6236 keV, just below the neutron separation energy of 6291 keV.Shell model calculations made using a small modification of the WBP interaction reproduce the negative-parity, 1-ph states rather well.

Compound-nuclear reaction cross sections from surrogate measurements

“…More recently, the Silicon Telescope Array for Reaction Studies (STARS) was developed (Lesher et al, 2010) and subsequent measurements were performed at the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. This system has been used to study a wide variety of topics in fundamental and applied nuclear physics, such as reactions (Clark et al, 2005;Burke et al, 2006;Lyles et al, 2007a;Gibelin et al, 2008;Scielzo et al, 2008;Allmond et al, 2009;Basunia et al, 2009;Lesher et al, 2009;Hatarik et al, 2010; and structure (Wiedeking et al, 2008a;2008b;Bender et al, 2009;Ressler et al, 2010). In the following sections, the apparatus and surrogate experiments that employ variants of the Weisskopf-Ewing approach are described.…”

“…11. The gadolinium region is well suited for tests of the surrogate nuclear reaction method because many stable Gd isotopes exist for which ðn; Þ cross sections have been directly measured (Beer and Macklin, 1988;Voignier, Joly, and Grenier, 1992), and sufficient nuclear-structure information is available to carry out complementary cross section calculations. For the even-even compound nuclei, high statistics could be collected for the E2 transitions from the 8 þ , 6 þ , 4 þ , and 2 þ states of the ground-state band.…”

“…Approaches such as the ANC (asymptotic normalization coefficient) method (Xu et al, 1994;Azhari et al, 1999;Gagliardi et al, 1999;Mukhamedzhanov, Gagliardi, and Tribble, 2001;Timofeyuk, Johnson, and Mukhamedzhanov, 2003;Timofeyuk and Descouvemont, 2005), Coulomb dissociation (Baur, Bertulani, and Rebel, 1986;Baur and Rebel, 1996;Baur, Hencken, and Trautmann, 2003), and the Trojan-horse method (Baur, 1986;Typel and Baur, 2003;Wolter and Typel, 2003;Baur and Typel, 2004;Pizzone and Spitaleri, 2008) have yielded valuable cross section information for various direct reactions. These methods focus on direct reactions, i.e., fast reactions (time scale % 10 À22 sec ) that involve simple rearrangements of the constituents of the target and projectile nuclei.…”

Cross-shell excitations inSi31

“…An early shell-model interaction to allow particles out of the 0p orbitals and/or into the 0f -1p shells was called WBP [30] and was adjusted to fit 20 F and 20 Na [31]. It was found [32,33] that the negative-parity states predicted for 32,34 P using the WBP interaction were computed much too high in excitation energy. Accordingly, the single-particle energies of the 0f 7/2 and 1p 3/2 orbitals were reduced by 1.8 and 0.5 MeV, respectively, relative the original WBP interaction.…”

Non-Hermitian dynamic strings and anomalous topological degeneracy on a non-Hermitian toric-code model with parity-time symmetry

“…The non-Hermitian Hamiltonians obeying Paritytime(PT )-symmetry as a complex extension of the (Hermitian) quantum mechanics can exist purely real energy spectrum, which was proposed by Bender and Boettcher [1]. It can exhibit spontaneous PT -symmetry breaking accompanied by transition from real to complex.…”