High-spin states in Au-188: Further evidence for nonaxial shape

The high-spin level structure of Au-188 has been investigated via the Yb-173(F-19,4n gamma) reaction at beam energies of 86 and 90 MeV. The previously reported level scheme has been modified and extended significantly. A new I-pi = 20(+) state associated with pi h(11/2)(-1) circle times nu i(13/2)(-2)h(9/2)(-1) configuration and two new rotational bands, one of which is built on the pi h(9/2) circle times nu i(13/2) configuration, have been identified. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around Au-188 for the pi h(9/2) circle times nu i(13/2) bands in odd-odd Au isotopes. Evidence for pi h(11/2)(-1) circle times nu i(13/2)(-1) structure of nonaxial shape with gamma < -70 degrees has been obtained by comparison with total Routhian surface and cranked-shell-model calculations.

Rotation alignment in neutron-rich Cr isotopes: A probe of deformed single-particle levels across N=40

Recent experiments have reached the neutron-rich Cr isotope with N = 40 and confirmed enhanced collectivity near this subshell. The current data focus on low-spin spectroscopy only, with little information on the states where high-j particles align their spins with the system rotation. By applying the projected shell model, we show that rotation alignment occurs in neutron-rich even-even Cr nuclei as early as spin 8 (h) over bar h and, owing to shell filling, the aligning particles differ in different isotopes. It is suggested that observation of irregularities in moments of inertia is a direct probe of the deformed single-particle scheme in this exotic mass region.

Dipole bands in nucleus Pm-139

High-spin states in nucleus Pm-139 have been studied using the reaction Cd-116(Al-27, 4n)Pm-139. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei (DCO) ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of Pm-139 are compared with those of the N = 78 isotone Eu-141 in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in Pm-139 may be magnetic rotational bands.

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

Effects of Pairing Correlations on Formation of Proton Halo in C-9

Properties for the ground state of C-9 are studied in the relativistic continuum Hartree-Bogoliubov theory with the NLSH, NLLN and TM2 effective interactions. Pairing correlations are taken into account by a density-dependent delta-force with the pairing strength for protons determined by fitting either to the experimental binding energy or to the odd-even mass difference from the five-point formula. The effects of pairing correlations on the formation of proton halo in the ground state of C-9 are examined. The halo structure is shown to be formed by the partially occupied valence proton levels p(3/2) and p(1/2).

缺中子奇质量数Au核高自旋态能级结构研究

利用能量为164-180MeV的35Cl束流，通过重离子核反应149Sm(35Cl,5n) 研究了179Au的高自旋态能级结构。实验进行了γ射线的激发函数、X-γ和γ-γ-t符合测量。基于实验测量结果，首次建立了179Au的1/2[660](πi13/2)转动带。结合已有的实验数据，着重讨论了奇-A Au核中1/2[660](πi13/2) 转动带的形变和带头激发能随中子数的变化。用能量为140MeV的29Si束流轰击159Tb金属靶，布居了183Au核的高自旋态。实验中要求至少有3个高纯锗和2个BGO探测器同时点火，在此符合条件下，记录高纯锗探测器探测到的γ射线的能量和相对时间、BGO探测到的γ射线的总能量和多重性。通过对实验数据的分析，扩展并更新了183Au的能级纲图。首次建立了183Au的πi13/2转动带的能量非优先带。分析并讨论了缺中子奇-A Au中πh9/2转动带的能量非优先带和πf7/2转动带间的相互作用

缺中子奇质量数Au核高自旋态能级结构研究

利用能量为164-180MeV的35Cl束流，通过重离子核反应149Sm(35Cl,5n) 研究了179Au的高自旋态能级结构。实验进行了γ射线的激发函数、X-γ和γ-γ-t符合测量。基于实验测量结果，首次建立了179Au的1/2[660](πi13/2)转动带。结合已有的实验数据，着重讨论了奇-A Au核中1/2[660](πi13/2) 转动带的形变和带头激发能随中子数的变化。用能量为140MeV的29Si束流轰击159Tb金属靶，布居了183Au核的高自旋态。实验中要求至少有3个高纯锗和2个BGO探测器同时点火，在此符合条件下，记录高纯锗探测器探测到的γ射线的能量和相对时间、BGO探测到的γ射线的总能量和多重性。通过对实验数据的分析，扩展并更新了183Au的能级纲图。首次建立了183Au的πi13/2转动带的能量非优先带。分析并讨论了缺中子奇-A Au中πh9/2转动带的能量非优先带和πf7/2转动带间的相互作用

Platinum nuclei: Concealed configuration mixing and shape coexistence

The role of configuration mixing in the Pt region is investigated. For this chain of isotopes, the nature of the ground state changes smoothly, being spherical around mass A~174 and A~192 and deformed around the midshell N=104 region. This has a dramatic effect on the systematics of the energy spectra as compared to the systematics in the Pb and Hg nuclei. Interacting boson model with configuration mixing calculations are presented for gyromagnetic factors, α-decay hindrance factors, and isotope shifts. The necessity of incorporating intruder configurations to obtain an accurate description of the latter properties becomes evident. © 2011 American Physical Society.

Pauli distorted double folded potential

The enhancement in the production of even-Z nuclei observed in nuclear fission has also been observed in fragments produced from heavy ion collsions. Beams of 40Ar, 40Cl, and 40Ca at 25 MeV/nucleon were impinged on 58Fe and 58Ni targets. The resulting fragments were detected using the MSU 4pi detector array, which had additional silicon detectors for better isotopic resolution. Comparison of the ratios of yields for each element showed enhancement of even-Z fragment production. The enhancement was more pronounced for reactions with a greater difference in the N/Z of the compound system. However, this effect was less for systems that were more neutron rich. The average N/Z for fragments also displayed an odd-even effect with a lower average N/Z for the even-Z fragments. This is related to the greater availability of neutron-poor isotopes for even-Z nuclei

Hypernuclear structure with the new Nijmegen potentials

Information on level density for nuclei with mass numbers A?20250 is deduced from discrete low-lying levels and neutron resonance data. The odd-mass nuclei exhibit in general 47 times the level density found for their neighboring even-even nuclei at the same excitation energy. This excess corresponds to an entropy of ?1.7kB for the odd particle. The value is approximately constant for all midshell nuclei and for all ground state spins. For these nuclei it is argued that the entropy scales with the number of particles not coupled in Cooper pairs. A simple model based on the canonical ensemble theory accounts qualitatively for the observed properties.

The tensor-kinetic field in nuclear collisions

The role of the tensor terms in the Skyrme interaction is studied for their effect in dynamic calculations where non-zero contributions to the mean-field may arise, even when the starting nucleus, or nuclei are even-even and have no active time-odd potentials in the ground state. We study collisions in the test-bed 16O-16O system, and give a qualitative analysis of the behaviour of the time-odd tensor-kinetic density, which only appears in the mean field Hamiltonian in the presence of the tensor force. We find an axial excitation of this density is induced by a collision.

Fundamental fermion masses from deformed SUq(2) triplets

A spectrum-generating q-algebra, within the framework of SUq(2), as firstly suggested by Iachello, is studied in order to describe the mass spectrum of three generations of quarks and leptons. The SUq(2) quantum group is a q-deformed extension of SU(2), where q = e(alpha) (with alpha real) is the deformation parameter. In this work, the essential use of inequivalent representations of SUq(2) is introduced. The inequivalent representations are labelled by (j, nu(0)), where j = 0, 1/2, 1, ... and nu(0) is a positive real number. A formula for the fermion masses M-m(j, nu(0)), with -j less than or equal to m less than or equal to j is derived. As an example, a possible scheme which corresponds to two triplets (j = 1) associated to up and down quarks is presented here in some detail. They are associated to different values of the deformation parameter, indicating a dependence of the charge Q on the parameter alpha. The masses of the charged leptons are treated in a similar way. The current results show that some mass relations for quarks and leptons found in the literature can be considered as approximations of the equations obtained in the j = 1 representations. The breaking of SUq(2) necessary to describe the Cabibbo-Kobayashi-Maskawa (CKM) flavor mixing is briefly discussed.

Properties of a new poly-ether-glycol copolymer.

Triblock copolymers are made of monomer segments, being the central part usually hydrophobic and the outer parts hydrophilic. By varying sizes, molecular weights and monomer types of the segments one obtains different final molecules, with different physico-chemical properties, which are directly related to the performance of the final product. Looking for new products to be used, among other possibilities, in biological applications, a new polymer (Figure 1) was synthesized by the Dow Chemical and studied by Size Exclusion Chromatography, Fourier Transformed Infrared Spectrometry, Small-angle X-ray Scattering (SAXS) and its cloud point was determined by measuring light transmittance. The studies showed low molecular polydispersivety, but different polarities in the macromolecules fractions. Due to the low solubility of Diol in water, a mixture of water/butyl diglycol was used as solvent. An extensive analysis by SAXS was performed for concentrations from 50 wt% to 80 wt% of Diol in solution. Small concentrations showed very low signal to noise ratio, making it impossible to be analysed. The scattering intensity including the form factor of polydisperse non-homogeneous spheres, and the structure factor of interacting hard spheres was fitted to the curves. As the polymer concentration is high, the fitting of form factors of direct and reverse micelles were compared. The results for direct micelles were better up to 80 wt%, whereas at 90 wt% and 95 wt% the curves were better fitted by reverse micelles. It might seem odd that direct micelles are present up to such high concentrations, but it might have been caused by the presence of butyl diglycol, which increases the solubility of Diol in water. The inner and outer radius of the micelles, electron density distribution, and interaction radius of the micelles were obtained. The polydispersivety increases with Diol concentration. Besides, the interaction radius increases with solvent concentration, even when reversed micelles are present. In the last case, accompanied by an increase of inner radius (water content), as there are fewer Diol molecules to involve the water nuclei, which become larger, further apart, and in less number.

Kollineare Laserspektroskopie an radioaktiven Praseodymionen und Cadmiumatomen

Die Analyse optischer Spektren liefert einen kernmodellunabhängigen Zugang zur Bestimmung der Kernspins, Ladungsradien und elektromagnetischen Momente von Atomkernen im Grundzustand und von langlebigen Isomeren. Eine der vielseitigsten Methoden zur optischen Spektroskopie an kurzlebigen Isotopen ist die kollineare Laserspektroskopie. Im Rahmen dieser Arbeit wurde zum einen die TRIGA-LASER Strahlstrecke am Institut für Kernchemie der Universität Mainz durch die Implementierung einer neuen offline Oberflächenionenquelle für hohe Verdampfungstemperaturen und eines Strahlanalysesystems weiterentwickelt. Zum anderen wurde kollineare Laserspektroskopie an kurzlebigen Praseodym- und Cadmiumisotopen an ISOLDE/CERN durchgeführt. Die neue Ionenquelle ermöglichte dabei den Test der kollinearen Laserspektroskopie an Praseodymionen am TRIGA-LASER Experiment. Die Spektroskopie der Prasdeodymionen motivierte sich aus der Beobachtung einer zeitlichen Modulation der EC-Zerfallsrate von wasserstoffähnlichem 140Pr58+. Für die Erklärung dieser sogenannten GSI Oszillationen wird unter anderem das magnetische Moment des Kerns benötigt, welches bislang noch nicht experimentell bestimmt wurde. Zudem wurde für wasserstoffähnliches 140Pr58+ überraschenderweise eine kleinere EC-Zerfallskonstante gemessen als für heliumähnliches 140Pr57+. Die Erklärung dieses Phänomens setzt ein positives magnetisches Moment voraus. Bei der Spektroskopie am COLLAPS Experiment wurden erstmals die magnetischen Momente von 135Pr, 136Pr und 137Pr vermessen. Aufgrund zu geringer Produktionsraten war die Spektroskopie des gewünschten Isotops 140Pr jedoch nicht erfolgreich. Die Untersuchung der Cadmiumisotope ist kernphysikalisch motiviert. In der Zinnregion erstrecken sich die Isotope über die beiden magischen Zahlen N=50 und N=82 bei gleichzeitiger Nähe des Z=50 Schalenabschlusses. Hier können verschiedene Kernmodelle getestet werden, die sich beispielsweise hinsichtlich der Stärke des N=82 Schalenabschlusses widersprechen. Diese Arbeit berichtet über erste Ergebnisse der Spektroskopie an Cadmiumatomen, die sich über die Isotope 106−124,126Cd sowie die zugehörigen langlebigen I=11/2− Isomere erstreckt. Die zuvor experimentell bekannten oder aus dem erweiterten Schalenmodell abgeleiteten Kernspins konnten für alle Isotope bis auf 119Cd bestätigt werden. Der Kernspin von 119Cd wurde eindeutig zu I=1/2 bestimmt. Die elektrischen Quadrupolmomente der Isomere zeigen ein bemerkenswert lineares Verhalten in Abhängigkeit von der Neutronenzahl und dies über die eigentliche Kapazität der 1h11/2 Unterschale hinaus. Die Änderungen der mittleren quadratischen Ladungsradien zeigen den auch an Indium- und Zinnisotopen beobachteten stetigen Verlauf. Der lineare Anteil passt sehr gut zu den Berechnung des Tröpfchenmodells in der Parametrisierung nach Berchidevsky und Tondeur. Die Differenzen der mittleren quadratischen Ladungsradien zwischen Grund- und isomeren Zustand der ungeraden Cadmiumisotope zeigen einen interessanten parabolischen Verlauf mit einem Minimum zwischen A=117 und A=119.

Outer crust of a cold non-accreting magnetar

The outer-crust structure and composition of a cold, non-accreting magnetar are studied. We model the outer crust to be made of fully equilibrated matter where ionized nuclei form a Coulomb crystal embedded in an electron gas. The main effects of the strong magnetic field are those of quantizing the electron motion in Landau levels and of modifying the nuclear single-particle levels producing, on average, an increased binding of nucleons in nuclei present in the Coulomb lattice. The effect of a homogeneous and constant magnetic field on nuclear masses has been predicted by using a covariant density functional in which induced currents and axial deformation due to the presence of a magnetic field that breaks time-reversal symmetry have been included self-consistently in the nucleon and meson equations of motion. Although not yet observed, for Ba 1016 G both effects contribute to produce different compositions - odd-mass nuclei are frequently predicted - and to increase the neutron-drip pressure as compared to a typical neutron star. Specifically, in such a regime, the magnetic-field effects on nuclei favor the appearance of heavier nuclei at low pressures. As B increases, such heavier nuclei are also preferred up to larger pressures. For the most extreme magnetic field considered, B=1018 G, and for the models studied, almost the whole outer crust is made of 4092Zr52.