Nuclear electric quadrupole moment of41Ca by laser-RF spectroscopy

Zeitschrift für Physik A Hadrons and nuclei - The nuclear electric quadrupole moment of41Ca, which contains a single neutron outside closed proton and neutron shells (N=Z=20) has been...     

Isomorphic shell model for closed-shell nuclei

The classical part of the isomorphic model for closed-shell nuclei is presented based on two physical assumptions, namely (a) the nucleons of a closed shell nucleus, considered at their most probable positions, are in an instantaneous dynamic equilibrium on spherical shells, and (b) the dimensions of the shells are determined by their close packing given that a neutron and a proton are represented by hard spheres of definite sizes. The first assumption leads to the instantaneous angular structure, and the second to the instantaneous radial structure of closed-shell nuclei. Applications of the model coming from this classical part alone and presented here are structural justification of all magic numbers, neutron (proton) and charge rms radii, nuclear densities of closed-shell nuclei, and Coulomb, kinetic, and binding energies. All the predictions are in good agreement with experimental data. A characteristic novelty of the isomphic model is that assumption (a) is related to the independent particle model, and assumption (b) to the liquid-drop model. The isomorphic model may provide a link between these two basic nuclear physics models since it incorporates features of both.     

The effect of the initial exciton numbers on <Superscript>54,56</Superscript>Fe(<Emphasis Type="Italic">p,xp</Emphasis>) Pre-Equilibrium Reactions

In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the ^54,56Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.     

Mass differences and neutron pairing in Ca,Sn and Pb isotopes

Various estimates of the even-odd effect of the mass shell of atomic nuclei are considered.Based on the experimental mass values of the Ca,Sn,and Pb isotopes,the dependence of the energy gap on the neutron number is traced and the relationship of this characteristic to the properties of external neutron subshells is shown.In nuclei with closed proton shells,effects directly related to neutron pairing and effects of nucleon shells are discussed.     

The (t, α) reaction on 121Sb and 123Sb

Angular distributions of α-particles from the (t, α) reaction on ¹²¹Sb and ¹²³Sb have been measured for incident tritons of 12 MeV. Levels up to excitation energies of 5.2 and 4.9 MeV in ¹²⁰Sn and ¹²²Sn, respectively, have been identified and analysed by the DWBA. Values of orbital angular momenta of the transferred protons have been assigned and spectroscopic factors deduced for all strongly excited levels. The extracted ground-state wave functions of the target nuclei have been compared with the calculated ones. A mixture of collective degrees of freedom is present in the low-lying states, weakly excited by the above very selective proton pick-up reaction. These states are populated by the pick-up of external protons (outer shells). At higher excitation energy (between 4 and 5 MeV) there are many strongly excited states populated by the proton pick-up from the Z = 50 proton core (inner shells); a predominantly 1p-1h character has been assigned to these states.     

The influence of Fe,Cu, SiO<Subscript>2</Subscript>, TiO<Subscript>2</Subscript>, and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in aqueous solution on proton relaxation times

Measurements of proton nuclear spin-spin and spin-lattice relaxation times are applied for determining the concentration of solid-phase nanoparticles in nanofluids. This approach is tested for metal oxides SiO₂, TiO₂, Al₂O₃ and metal-carbon nanoparticles of 3d-metals Fe and Cu. It is shown that the sensitivity of the method for determining concentrations of 3d-metals is much higher than for oxides (by 2–4 orders of magnitude). It is revealed that measurement of the proton spin-spin relaxation time allows one to determine the concentration of Cu nanoparticles to 0.0001 mg/ml and that of Fe nanoparticles to 0.00001 mg/ml.     

Route to islands of stability of superheavy elements

Problems concerning the existence of hypothetical superheavy elements for which theoretical nuclear models predict high stability with respect to various modes of radioactive decay are discussed. The synthesis of superheavy nuclei and the possibilities for performing experiments aimed at detecting rare events of their production and decay in heavy-ion beams are considered. Experimental results suggesting a considerable increase in the lifetime of nuclei as they approach the closed proton and neutron shells determining the islands of stability of superheavy elements are presented.     

Double-Blocking Effects in Odd-odd Superdeformed Nucleus 194Tl

Six superdeformed bands of odd-odd nucleus ¹⁹⁴Tl in A～190 mass region are studied using the particle-number conserving method for treating the cranked shell model with pairing interactions. Calculated results agree with experiments very well. Based on our calculation the configurations of the six superdeformed bands are assigned and the influence of blocking effects of proton and neutron on moments of inertia is investigated in detail. The variation of moments of inertia with rotational frequency is mainly attributed to the intruder shells (neutron N=7 and proton N=6), whereas the contributions to moment of inertia from other shells remain almost unchanged with rotational frequency.     

Interference effects in proton scattering on <Superscript>15</Superscript>N nuclei at intermediate energies

The differential cross section for proton scattering on ¹⁵N nuclei is calculated within Glauber diffraction theory at energies of 0.2, 0.6, and 1.0 GeV. Use is made of the shell-model wave function for the ¹⁵N nucleus. The contribution of single and double collisions to the Glauber operator Ω is taken into account. The sensitivity of the differential cross sections to the contributions of scattering on nucleons from different shells, to the parameters of the elementary pN amplitude, and to the energy of projectile protons is investigated. It is shown that the interference between amplitudes corresponding to different collision multiplicities, as well as between the amplitudes for scattering on nucleons from different shells, determines special features of the cross section.     

How to catch a ‘fat’ proton

We argue that high-multiplicity events in proton–proton or proton–nucleus collisions originate from large-size fluctuations of the nucleon shape. We discuss a pair of simple models of such proton shape fluctuations. A “fat” proton with a size of 3 fm occurs with observable frequency. In light of this result, collective flow behavior in the ensuing nuclear interaction seems feasible. We discuss the influence of these models on the parton structure of the proton.     

核衰变产生的X射线和俄歇电子数据计算

核衰变过程中,内转换电子发射和电子俘获能在原子电子壳层内留下空穴.其他原子电子壳层的电子将填补这些空穴,其原子电子位置将重排,并发射X射线和俄歇电子.X射线和俄歇电子的能量由原子电子结合能计算得到,X射线和俄歇电子的强度分别由内转换电子发射和电子俘获在原子电子壳层内留下的空穴数,X射线荧光产额,和空穴转移系数计算得到.本文简要介绍核衰变产生的X射线和俄歇电子数据的计算方法、计算程序与工作流程,并以核衰变为例说明其具体应用和简要讨论与总结.     

Leading and higher twists in proton,neutron and deuteron unpolarized structure functions F<Subscript>2</Subscript>

We summarize the results of a recent global analysis of proton and deuteron F₂ structure function world data performed over a large range of kinematics, including recent measurements done at JLab with the CLAS detector. From these data the lowest moments (n≤10) of the unpolarized structure functions are determined with good statistics and systematics. The Q² evolution of the extracted moments is analyzed in terms of an OPE-based twist expansion, taking into account soft-gluon effects at large x. A clean separation among the leading- and higher-twist terms is achieved. By combining proton and deuteron measurements the lowest moments of the neutron F₂ structure function are determined and its leading-twist term is extracted. Particular attention is paid to nuclear effects in the deuteron, which become increasingly important for the higher moments. Our results for the non-singlet, isovector (p-n) combination of the leading-twist moments are used to test recent lattice simulations. We also determine the lowest few moments of the higher-twist contributions, and find these to be approximately isospin independent, suggesting the possible dominance of ud correlations over uu and dd in the nucleon.     

The role of Fermi motion and quark exchange as a nuclear medium effect in the nuclear structure function of 3He, 3H nuclei and their EMC effects

To extract the nuclear structure function of light nuclei like ³He and ³H, the convolution of proton and neutron structure functions in the conventional approach could not explain the modification of nuclear structure functions of these nuclei because of some nuclear medium effects. There are some models that have some success to explain the modification of nuclear structure functions in limited x range. So in this investigation the quark exchange model is considered to extract the nuclear medium effect of this phenomenon (quark exchange effect) for nuclear structure functions of ³He and ³H nuclei. The Fermi motion part of the nuclear structure functions for these nuclei is extracted by taking the GRV’s neutron and proton structure functions in the conventional approach. So the nuclear structure functions and the EMC ratios of ³He and ³H nuclei are calculated by considering both Fermi motion and the nuclear medium effect of quark exchange. Finally the extracted results are compared with available data.     

Two proton transfer reactions between pairing rotational states with 104 MeV16O on142Nd,144Sm,148Sm and152Sm

(¹⁶O,¹⁴C) reactions on target nuclei with open proton shells, which are members of protonpairing rotational bands have been studied. For all target nuclei strong transitions to the ground states are observed. The reduced groundstate transition strength's (after removal ofQ-value dependence) are almost equal for all four target nuclei. Additional data on (¹⁶O,¹⁵N), (¹⁶O,¹³C) and (¹⁶O,¹²C) reactions are used to discuss the enhancement in the two proton transfer.     

Diffractive dissociation of deuterons and exotic nuclei <Superscript>6</Superscript>He and <Superscript>19</Superscript>C

A theory is developed for describing the diffractive dissociation of loosely bound two-cluster nuclei in the nuclear and Coulomb fields of nuclei having a diffuse boundary. The energy spectra of charged products of the breakup of ²H, ⁶He, and ¹⁹C nuclei are calculated on the basis of the proposed approach, and the results are found to be rather sensitive to nuclear structure. For some angles of neutron and proton emission from the reaction ¹²C(d, np)¹²C, the calculated cross sections are in satisfactory agreement with the results of kinematically complete experiments performed recently to study the breakup of intermediate-energy deuterons.     

EPR and ENDOR investigations of Ge,Sn and Pb impurities in CdSe

Electron paramagnetic resonance (EPR) experiments of light activated Ge, Sn and Pb impurities in wurtzite type CdSe crystals are presented. These²S_1/2 centres exhibit a large hyperfine structure which shows a variation with temperature. 25 shells of neighbour nuclei are resolved for CdSeSn by means of the Electron nuclear double resonance (ENDOR) technique. All shells belong to one of three distinct shell symmetries of the lattice thus confirming a high symmetry defect. Additional Sn respectively Ge related spectra are described and interpreted as complex centres correlated with lithium.     

Analysis of <Emphasis Type="Italic">p</Emphasis><Superscript>10</Superscript>B scattering within Glauber theory

The differential cross sections for p ¹⁰B scattering are calculated at the energies of 197, 600, and 1000 MeV within Glauber theory. The contributions of single and double collisions are taken into account in the multiple-scattering operator. The contributions of proton collisions with nucleons belonging to various (1s, 1p) shells are estimated in the single-scattering cross sections. A comparison with experimental data and with the result of calculations in the distorted-wave Born approximation (DWBA) at 197 MeV showed that the differential cross sections for p ¹⁰B scattering are adequately described in the region forward scattering angles.     

协变密度泛函理论中的张量力效应

张量力是核子-核子相互作用的重要成分,被认为是理解奇特原子核中壳结构演化规律的关键要素。然而,目前对于核介质中的张量力及其效应的定量认识,仍存在很多亟待解决的关键问题。着重梳理了在原子核密度泛函理论框架下,研究有效相互作用中的张量力成分以及相应的张量力效应的相关工作,重点包括:基于相对论Hartree-Fock理论,以同位素链中的质子幻数壳演化为例,定量提取与分析其中的张量力效应;以及基于第一性原理的相对论Brueckner-Hartree-Fock理论,以中子滴单粒子能谱中的自旋-轨道劈裂演化为例,提出与张量力效应相关联的"准实验数据"。最后,展望原子核密度泛函理论今后可能的发展策略。Tensor force is one of the most important components of the nucleon-nucleon interaction. It plays a critical role in understanding the shell evolution in exotic nuclei. However, there are still several puzzles concerning the tensor force and its effects in the nuclear medium. In this paper, we mainly focus on the studies of tensor force in the effective interactions and its effects in finite nuclear systems within the scheme of nuclear density functional theory. In particular, we highlight the recent developments, including the quantitative analysis of tensor effects in the relativistic Hartree-Fock theory by taking the evolution of proton magic shells in the isotopic chains as an example, and the "meta-data" of tensor effects provided by the ab initio relativistic Brueckner-Hartree-Fock theory by taking the evolution of spin-orbit splitting in the single-particle spectra of neutron drops as an example. Perspectives are focused on the possible strategies for the future developments of nuclear density functional theory.     

Physical properties of hot, dense matter: The bulk equilibrium approximation

Starting from a Skyrme effective nucleon-nucleon interaction, we calculate the properties of hot matter at densities up to a little beyond that of nuclear matter. We neglect effects associated with finite nuclear size, such as surface and Coulomb energies, but include all effects associated with the bulk properties of the neutron-proton matter over a range of proton concentrations. The region of coexistence of two distinct nuclear phases is mapped out, as a function of the average proton fraction of the two-phase mixture. We present the neutron and proton chemical potentials, and the densities and proton fractions of the two coexisting phases, as functions of density and temperature. The density dependence of the nuclear contribution to the pressure is given along isotherms for a range of proton fractions. Including electron, positron and photon contributions to the entropy, we calculate the density dependence of the pressure along adiabats, and discuss the distribution of the entropy among the components. Some information is also given about hot matter in β-equilibrium. Comparison is made with earlier work.     

Proton radius,Darwin-Foldy term and radiative corrections

We discuss the role of the so-called Darwin-Foldy term in the evaluation of the proton and deuteron charge radii from atomic hydrogen spectroscopy and nuclear scattering data. The question of whether this term should be included or excluded from the nuclear radius has been controversially discussed in the literature. We attempt to clarify which literature values correspond to which conventions. A detailed discussion of the conventions appears useful because a recent experiment [R. Pohl et al., Nature 466, 213 (2010)] has indicated that there is a discrepancy between the proton charge radii inferred from ordinary (“electronic”) atomic hydrogen and muonic hydrogen. We also investigate the role of quantum electrodynamic radiative corrections in the determination of nuclear radii from scattering data, and propose a definition of the nuclear self energy which is compatible with the subtraction of the radiative corrections in scattering experiments.