Evolution of nuclear spectra with nuclear forces

We first define a series of NN interaction models ranging from very simple to fully realistic. We then present Green's function Monte Carlo calculations of light nuclei to show how nuclear spectra evolve as the nuclear forces are made increasingly sophisticated. We find that the absence of stable five- and eight-body nuclei depends crucially on the spin, isospin, and tensor components of the nuclear force.     

Low-energy nuclear reactions with double-solenoid-based radioactive nuclear beam

The University of Notre Dame, USA (Becchetti et al, Nucl. Instrum. Methods Res. A505, 377 (2003) and later the University of São Paulo, Brazil (Lichtenthaler et al, Eur. Phys. J. A25, S-01, 733 (2005)) adopted a system based on superconducting solenoids to produce low-energy radioactive nuclear beams. In these systems the solenoids act as thick lenses to collect, select, and focus the secondary beam into a scattering chamber. Many experiments with radioactive light particle beams (RNB) such as ⁶He, ⁷Be, ⁸Li, ⁸B have been performed at these two facilities. These low-energy RNB have been used to investigate low-energy reactions such as elastic scattering, transfer and breakup, providing useful information on the structure of light nuclei near the drip line and on astrophysics. Total reaction cross-sections, derived from elastic scattering analysis, have also been investigated for light system as a function of energy and the role of breakup of weakly bound or exotic nuclei is discussed.     

Coriolis anti-pairing theory of nuclear rotations nuclear meissner-effect

It is shown that the ground-state rotational bands of spherical nuclei are formed by a gradual alignment of the angular momenta of valence nucleons along the rotation axis. The predicted spin and excitation energy values of the first rotational state in ²¹²Po nucleus are J = 16⁺ and E = 2.91 MeV which is in reasonable agreement with the experimental data (J = (18⁺), E = 2.93 MeV).     

开发没有核污染的核能源

化学家与物理学家的合作在科学发现史上是非常重要的.为了使得科学发现更容易被科学界的主流所接受我们必须有多方面的理论预言,由不同的,独立的实验结果来加以证实.开发没有核污染的核能源,这样-个辉煌的目标已成为世界范围内不懈的努力的真正动力.决定性的下一步是建立自持发热的反应堆和探测从金属氢化物(氘化物)发射的中微子.     

Density content of nuclear symmetry energy from nuclear observables

The nuclear symmetry energy at a given density measures the energy transferred in converting symmetric nuclear matter into the pure neutron matter. The density content of nuclear symmetry energy remains poorly constrained. Our recent results for the density content of the nuclear symmetry energy, around the saturation density, extracted using experimental data for accurately known nuclear masses, giant resonances and neutron-skin thickness in heavy nuclei are summarized.     

Dynamic nuclear polarization and nuclear orientation in an antiferromagnet

Dynamic nuclear polarization is a well established technique which has been used to produce polarized targets for experiments in nuclear physics. This paper suggests experiments of a similar type but involving the nuclear magnetic resonance of two isotopes, one stable and the other radioactive. The substance is an antiferromagnet, dysprosium phosphate, at temperatures below the Néel point, where line widths are comparatively small. The effect may be detected through changes in the rate of gamma ray emission observed by a nuclear orientation experiment.     

High-frequency dynamic nuclear polarization in the nuclear rotating frame

A proton dynamic nuclear polarization (DNP) NMR signal enhancement (epsilon) close to thermal equilibrium, epsilon = 0.89, has been obtained at high field (B(0) = 5 T, nu(epr) = 139.5 GHz) using 15 mM trityl radical in a 40:60 water/glycerol frozen solution at 11 K. The electron-nuclear polarization transfer is performed in the nuclear rotating frame with microwave irradiation during a nuclear spin-lock pulse. The growth of the signal enhancement is governed by the rotating frame nuclear spin-lattice relaxation time (T(1rho)), which is four orders of magnitude shorter than the nuclear spin-lattice relaxation time (T(1n)). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T(1rho) and is not limited by the much slower lab frame nuclear spin-lattice relaxation rate (1/T(1n)). The increased repetition rate allowed in the nuclear rotating frame provides an effective enhancement per unit time(1/2) of epsilon(t) = 197. The nuclear rotating frame-DNP experiment does not require high microwave power; significant signal enhancements were obtained with a low-power (20 mW) Gunn diode microwave source and no microwave resonant structure. The symmetric trityl radical used as the polarization source is water-soluble and has a narrow EPR linewidth of 10 G at 139.5 GHz making it an ideal polarization source for high-field DNP/NMR studies of biological systems.     

Dynamic nuclear polarization and nuclear orientation in terbium vanadate

Dynamic nuclear polarization is a well established technique, which has been used to produce polarized targets for experiments in nuclear physics. This paper suggests new experiments, involving the nuclear magnetic resonance of two isotopes, one stable, the other radioactive, in an antiferromagnet, terbium vanadate. At temperatures well below the Néel point, the line widths should be comparatively small. Resonance may be detected through changes in the rate of gamma-ray emission observed by a nuclear orientation experiment.     

New approach to nuclear binding energy in integrated nuclear model

In this paper, the integrated nuclear model is introduced and a binding energy formula based on this model is presented. The binding energies of most nuclides in this model are compared with available experimental values and also with values from the liquid drop model (LDM).     

Nuclear charge radii,nuclear moments,and nuclear structure

New and systematic measurements of nuclear charge radii and nuclear moments are providing a deeper insight into properties of nuclei. In this article, the implications of these new measurements on our understanding of collective properties of nuclei are discussed.     

Interference between nuclear resonance and nuclear Thomson scattering of photons

The elastic differential scattering cross section from ⁵⁵Mn has been measured at θ = 140° with E_γ = 5.5–11.4 MeV photons. Evidence for destructive interference between nuclear resonance (NR) scattering and nuclear Thomson (NT) scattering has been obtained.     

Studies of nuclear second moments for pre-equilibrium nuclear reaction theories

The nuclear second moments, important inputs to pre-equilibrium reaction theories, are evaluated by assuming a simple model. The positive definite nature of the second moments is examined, and the nuclear level densities are calculated using positive definite second moments.     

The effect of conventional nuclear binding on nuclear structure functions

We show that Fermi motion (including the effect of nucleon binding energy), together with a simple ansatz for the dependence of the nucleon structure function on its invariant mass, can explain the major features of recent nuclear structure function data. The close relationship of this work to the earlier explanations of the EMC effect based on an enhancement of the virtual pion field of the nucleus is discussed.     

One-body nuclear friction

We have calculated the velocity dependent forces acting between two nuclei that arise due to one-body mechanism of nuclear excitation when they are dragged against one another with constant velocity. The nuclear friction coefficients are then extracted from the velocity dependence of these forces which is found to be strongly linear. The one-body force is calculated by solving the time-dependent Schrödinger equation for all the occupied single-particle states of a nuclear system in a central collision. Each nucleus in this model is assumed to be described by a single-particle Woods-Saxon potential filled with 40 nucleons each. The magnitude of the resulting one-body friction is found to be in between the proximity and surface frictions. The proximity-friction is too small by about an order of magnitude. To check this result, we calculated the one-sided flux from one nucleus to the other. The friction force connected to this flux (i.e. the one-body exchange friction) turns out to be about half or less than the one body friction. We conclude that theproximity-friction grossly underestimates the one-body exchange friction. Furthermore,inelastic excitations are at least as important for one-body dissipation at distances beyond the touching point as is particle exchange.