Shell-model calculations for the properties of nuclei with A = 86–100 near the proton drip line

Extensive shell-model calculations in the mass range A = 86–100 on the neutron-deficient side of the nuclear chart are performed. The complete spectra of all isotopes are computed and compared to experimental excitation energies where available. Beta decay half lives are evaluated with both free and effective Gamow-Teller operators. The binding energies are obtained using a five parameter fit in addition to the shell-model energies. From the binding energies we deduce the proton drip line.     

Data on the Neutron–Neutron Scattering Length from the nd-Breakup Reaction at En = 8 MeV and En = 11 MeV

Physics of Atomic Nuclei - A kinematically complete experiment devoted to studying the $$nd$$ -breakup reaction at energies of 8 and 11 MeV via detecting all three secondary particles was...     

Possibility of Studying Neutron–Neutron Correlations in Halo Nuclei

An experimental investigation of the reaction of core pickup from ⁶He and ¹¹Li two-neutronhalo nuclei is proposed. In such experiments, neutron–neutron correlations in a halo nucleus will be assessed on the basis of the energy of a neutron–neutron quasibound state. A detailed kinematical simulation of the reaction ⁶He + ²H → ⁶Li + (nn) →⁶ Li + n + n is performed. It is shown that the energy of the quasibound state in question can determined from the shape of the energy spectrum of neutrons originating from the breakup of this state. In the proposed exclusive experiment, a beam of ⁶He (¹¹Li) nuclei with an energy of about 5 to 10 MeV per nucleon interacts with a deuterated-polyethylene target. This will permit detecting charged particles (⁶Li and ¹¹Be) and a neutron. On the basis of determining the energy of the neutron–neutron quasibound state, it will become possible to estimate the effective attraction between the valence neutrons in the field of the third particle (core).     

Transition parameters of Li-like ions(Z = 7–11) in dense plasmas

The energy levels, transition energies, transition probabilities, weighted oscillator strengths, and line strengths of Lilike ions(Z = 7–11) in dense plasmas are investigated in this work. The relativistic effects and electron correlation effects are described by the MCDHF method. The ion sphere model is applied to include the dense plasma screening effect. The ground configuration 1 s~22 s and the excited 1 s~22 p, 1 s~23 l(l = 0–2) are considered. The configuration sets are enlarged until n = 7 where the calculated energy levels have converged. The critical free electron densities of 1 s~23 d states are estimated.Except for 1 s~23 s–1 s~23 p transitions, the transition energies for Δn = 0 increase, and for Δn ≠ 0 decrease with increasing free electron densities. For 1 s~23 s–1 s~23 p transitions, the spectra show blue-shift at lower free electron densities and red-shift at higher free electron densities, and the energy level crossing phenomens are observed at higher free electron densities.     

A self-consistent mean-field study of Z = 120 nuclei and α-decay chains of 292,298,299,300,304120 isotopes

A self-consistent mean-field investigation is done to test the model accuracy, model dependence, and the dependence on different model parameters in the study of superheavy nuclei. This is done within the self-consistent mean-field models-the Skyrme-Hartree-Fock-Bogoliubov (HFB), and the Relativistic-Hartree-Bogoliubov (RHB) with density-dependent couplings. A systematic comparison is made with experimental data, as well as with the macro-microscopic Finite Range Droplet Model(FRDM). The bulk ground state properties and the microscopic structure of Z=120 superheavy nuclei are investigated. Further investigation is made of α-decay series for the five isotopes ^{292,298,299,300,304}120 of Z=120 nuclei. A spontaneous fission investigation is done to account the number of α-decay before spontaneous fission starts. The experimental data available for α-decay energies and half-lives are produced reasonably. The RHB model with NL3* parameter set, and with ImSahu and UNIV2 formula to calculate the α-decay half-lives is found to be the best suited for accurately predicting the ground state properties and the α-decay half-lives of the superheavy nuclei.     

Decay properties of neutron-deficient nuclei in the region Z = 86–92

Neutron deficient isotopes of elements Z = 86-92 have been produced by heavy-ion fusion reactions ¹²C + ²⁰⁸Pb, ²⁰⁹Bi, ²²Ne + ²⁰⁸Pb, ⁵¹V + ¹⁷⁰Er, and ⁵⁰Ti + ¹⁷⁰Er. The evaporation residues were investigated by means of α- and α-γ-spectroscopy after in-flight separation from the projectile beam by the velocity filter SHIP and implantation into a 16-strip position-sensitive Si-detector. New or improved decay data for ^{225, 226}U, ^{216, 217m, 218}Pa, ^{215, 216, 217}Th, ^{214, 215, 216, 216m}Ac, ²¹⁴Ra and ²¹³Rn have been obtained. Received: 5 April 2000 / Accepted: 28 July 2000     

End modes in arrays of modulated Su–Schrieffer–Heeger chains

In this article, an extended and modulated version of the classic Su–Schrieffer–Heeger model is analysed. The nature of the end modes and the effect of cyclic modulation of the hopping parameters are studied in detail. The analysis is extended to the case of an array of linear chains described by the Su–Schrieffer–Heeger model, where the robustness of the end states for a large range of coupling strengths between the chains is found.     

Optical Coefficients of Nanoscale Copper Films in the Range of 9–11 GHz

Optics and Spectroscopy - The reflectance, transmittance, and absorption coefficient of ultrathin copper films on a quartz substrate have been measured in a waveguide at frequencies of 9–11...     

Theoretical Analysis of Neutron Double-Differential Cross Sections of n ＋^9Be Reactions

By using the nuclear reaction model for light nuclei, the calculations of the double-differential cross sections of outgoing neutrons from n ＋^9Be reactions are performed. The total outgoing neutrons are only come from the （n, 2n）2a reaction channel. The （n, 2n）2a reaction channel is achieved through six different reaction approach, which are illustrated in this paper. The calculated results agree very well with the measured data at En = 7.1, 8.09, 8.17, 9.09, 9.97 and 10.26 MeV, because the updated level schemes related to the n ＋ ^9Be reactions have been employed in this calculations.     

Determination of the Galaxy age by the method of uranium–thorium–plutonium isotopic ratios

The dependence of the Galaxy age (Т _G), as determined by the method of uranium–thorium isotopic ratios, on the parameters of the nucleosynthesis model is studied within the theory of galactic nucleosynthesis. It is shown that ТG depends strongly both on the scenario of the production of nuclei in the r-process and those features of neutron-rich nuclei that are used in the respective analysis and on galactic-nucleosynthesis parameters. The effect of a sudden nucleosynthesis spike before the formation of a solar system on the Galaxy age is evaluated. The region of admissible values of the parameters of galacticnucleosynthesis theory is discussed. The method of uranium–thorium isotopic ratios is supplemented with the ²⁴⁴Pu/²³⁸U ratio for yet another cosmochronometer pair, and the Galaxy age is estimated on the basis of the model modified in this way.     

Detailed Investigation of Neutron–Neutron Angular Correlations in the Spontaneous Fission of $${}^{{252}}$$ Cf

Physics of Atomic Nuclei - New precise measurements of angular neutron–neutron ( $$nn$$ ) correlations in the spontaneous fission of $${}^{252}$$ Cf were performed with the aim of studying...     

Surface tension of hydrocarbon chains at the liquid–vapour interface

Molecular dynamics simulations were performed at constant temperature to obtain the surface tension of hydrocarbon chains at the liquid–vapour interface. The Ewald sum was used to calculate the dispersion forces of the Lennard–Jones potential to take into account the full interaction. The NERD and TraPPE_UA flexible force field models were used to simulate molecules from ethane to hexadecane along the coexistence curve. The simulation results for the TraPPE_UA model are in good agreement with experimental data, whereas the NERD model predicts slightly higher values.     

Neutron diffraction study of the CeFeSi-type RTiGe compounds (R=Pr,Nd, Tb–Er)

Neutron diffraction experiments were carried out on polycrystalline RTiGe (R=Pr, Nd, Tb–Er) samples. These compounds crystallise with the tetragonal CeFeSi-type structure (space group P4/nmm). This structure is closely related to the ThCr₂Si₂-type and can be described as “BaAl₄ blocks” connected via R–R contacts (“W blocks”). All the compounds are antiferromagnetic. PrTiGe and NdTiGe are characterised by an easy-plane sine-modulated structure characterised by a wave vector k=0,0,q_z=0.242 and 0.334 below 62 and 128 K, respectively. Below 80 K, NdTiGe exhibits a commensurate arrangement, which consists on ferromagnetic (0 0 1) Nd layers coupled antiferromagnetically along the c direction with the sequence ++−−. This commensurate magnetic ordering also occurs in TbTiGe, DyTiGe, HoTiGe and ErTiGe below 312, 185, 124 and 36 K, respectively. In the first three compounds (R=Tb−Ho), the magnetic moment is aligned along the c-axis whereas it is localised in the basal plane in ErTiGe. In all the RTiGe compounds, the magnitude of the ordered moments at 2 K amounts nearly to the free ion magnetic moment (gJ) values for the respective R³⁺ ions.     

On the equilibrium isotopic composition of the thorium–uranium–plutonium fuel cycle

The equilibrium isotopic compositions and the times to equilibrium in the process of thorium–uranium–plutonium oxide fuel recycling in VVER-type reactors using heavy water mixed with light water are estimated. It is demonstrated thEhfat such reactors have a capacity to operate with self-reproduction of active isotopes in the equilibrium mode.     

Excitation Energies of 1s^2 ns （6 ≤ n ≤ 9） States for Lithium-Like Systems from Z = 11 to 20

The non-relativistic energies of 1s^2 ns (6 ≤ n ≤ 9) states for the lithium-like systems from Z = 11 to 20 are calculated by using a full-core-plus-correlation (FCPC) method. The relativistic and mass-polarization effects on the energy are calculated by the first-order perturbation corrections. The correction from the quantumelectrodynamics effect is also included using effective nuclear charge. Based on these results and the quantum defect theory, the quantum defects of 1s^2ns series for these ions, as a function of energy, are determined. The comparisons between the ionization potentials for 1s^2ns states (6 ≤ n ≤ 9) obtained by the FCPC method and the semi-empirical method are carried out. The results show that their agreement is very well and the energies of all discrete states (n ≥ 10) below the ionization threshold of this series for the ions can be predicted by using their quantum defects.