Ni Nuclei Research Articles

Changes induced by the presence of Zn or Ni impurity at Cu sites in CuAlO 2 delafossite

A semiconducting delafossite compound CuAlO 2 containing either Zn or Ni impurity substituting for a Cu position has been investigated. The electronic structure and the electric field gradients (EFGs) for both donor (Zn) and acceptor (Ni) doped systems have been calculated using a full potential linear augmented plane-wave method with generalized gradient approximation accounting for the exchange and correlation effects. The results clearly indicate that the presence of Zn impurities changes the electric properties of CuAlO 2 by producing n-type semiconductivity, in a similar way as we have previously shown for the Cd impurity. In the case when Ni substitutes Cu the results of calculations indicate p-type semiconductivity in the material. Despite the fact that both Zn and Ni exhibit a similar hybridization scheme for the bonding with neighboring oxygens, their d electron clouds have different shapes due to deficit (Ni) and excess (Zn) of the d z 2 electrons. This effect is responsible for the large difference between the EFG values calculated at the Ni and Zn nuclei in the compound.

Gamma-ray spectroscopy of the neutron-rich Ni region through heavy-ion deep-inelastic collisions

Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T 1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.

Tip growth model of carbon tubules grown on the glass substrate by plasma enhanced chemical vapor deposition

Morphology of Ni tips and microstructures of carbon tubules were investigated and a growth model for carbon tubules was proposed. Triangular shaped Ni tips and piled-cone structure of carbon tubules were observed at the growth temperature of 500 °C. At the high growth temperature of 620 °C, smoothened edge shaped Ni tips were found and graphite layers became parallel to the growth direction as they were close to the outer wall of carbon tubules. Formation of Ni nuclei for carbon tubule growth was explained by NH3 pre-etching and precipitation of carbon atoms diffused from the surface of the Ni layer. A preferential growth of carbon tubules was observed and explained with the Ni orientation and size effect. A modified tip growth model based on surface diffusion was proposed for the growth mechanism of carbon tubules.

Description of the 56Ni ground state with a few symmetry projected general complex Hartree–Fock–Bogoliubov determinants

The ground state of the mid pf-shell nucleus 56Ni is described in the framework of a symmetry-projected complex mean-field theory in which the desired symmetry properties are exactly projected from the most general Hartree–Fock–Bogoliubov type determinants. This few determinant method is applied for the first time in a full 1 p0 f-shell model space. In the calculations the FPD6 effective interaction was used. It turns out that the use of only a few such generalized determinants is sufficient to give an excellent result. We compare the result with that of the quantum Monte Carlo approach, as well as with recently performed exact shell-model diagonalizations.

Beta decay of 56Cu

The proton-rich isotope 56Cu was produced at the GSI On-Line Mass Separator by means of the 28Si( 32S, p3n) fusion–evaporation reaction. Its β-decay properties were studied by detecting β-delayed γ rays and protons. A half-life of 93±3 ms was determined for 56Cu. Compared to the previous work, six new γ rays and three new levels were assigned to the daughter nucleus 56Ni. The measured Gamow–Teller strength values for five 56Ni levels are compared to shell-model predictions.

Variational approach to shape coexistence in 56Ni

Results are presented concerning shape coexistence and neutron–proton correlations at low and high spins in the N=Z nucleus 56Ni obtained within the complex version of the Excited Vampir variational approach. The coexistence of small and moderately deformed oblate and prolate configurations, strongly mixed in some cases, may explain the irregularities observed for the yrast line, as well as the presence of other nonyrast states connected with them by E2 or Ml transitions. The first deformed band is well reproduced and predictions on the structure of next deformed bands are presented. These are the first microscopic calculations for 56Ni including in the model space the 0g 9/2 and 1d 5/2 spherical orbitals besides the full pf-shell. Contaminations due to the center of momentum motion are discussed and a rough method to eliminate them at least approximately is presented.

TOTAL REACTION CROSS SECTIONS FOR 100-MeV ALPHA PARTICLES USING SEMI-PENOMENOLOGICAL NUCLEON DENSITY DISTRIBUTION

Theoretical study of α total reaction cross-sections for 50 Ti , 52 Cr , 54,58 Fe , and 58,64 Ni nuclei at 100 MeV is presented. Working within the framework of Coulomb modified Glauber model, we calculate α reaction cross-sections in terms of the phenomenological N-α amplitude using the semi-phenomenological nucleon density distribution proposed by Gambhir and Patil [Z. Phys.A324 (1986) 9]. We find that the semi-phenomenological density reproduces the observed behaviour of the reaction cross-sections for the isotopes and isotones quite satisfactorily.

Spectroscopy of 44,46Ti with the Binary Reaction Spectrometer and Euroball

A first experiment was performed with the Binary Reaction trigger Spectrometer (BRS) for Euroball, as second last experiment of phase III. The reaction 24Mg(32S, 56Ni*) at E = 163.5 MeV was chosen in order to populate a specific hyperdeformed resonance state in the compound nucleus 56Ni* at E* = 84 MeV (Jπ = 46+) and to investigate the spectroscopy of its binary descendents. The experimental setup combined the γ-detector array Euroball III, without the phase I Ge detectors, the two large-area gas detector telescopes of the BRS at forward angles and 31 of the 40 detectors of the 4π silicon ball EUROSiB (now called ROSiB) at backward angles. We report on results of binary reaction triggers collected with one BRS telescope. Binary events are separated from evaporation residues due to (i) the large laboratory scattering angles of the detected reaction fragments, the opening angle of the BRS telescope being θ = 12 ° – 46 °, and (ii) by means of particle identification in the telescope. In this paper channels with emission of 8Be plus two protons and of 12C will be discussed.

The numerical calculations of energy spectrum of <sup>16</sup>C and <sup>58</sup>Ni nuclei in the adiabatic approach

Within the framework of the hyperspherical adiabatic approach the numerical calculations of the energy levels of 16 C and 58 Ni nuclei have been performed. The effective field is created by all the nucleons and this field is modelled by the Woods-Sakson potential. The nucleon-nucleon interaction of valency nucleons is simulated by the zero-radius interaction potential. The energies of excited states of twin nucleons of 16 C and 58 Ni nuclei are calculated, these energies agree with available experimental data.

The structure at the interface of Ni/Pd superlattices with different crystal orientations estimated from molecular dynamics simulation

Molecular dynamics simulations of the formation process of an Ni/Pd film were performed by employing the embedded atom method with high (10 eV) and low (0.1 eV) kinetic energies of incident atoms for two different crystal orientations: fcc (1 1 1) and fcc (1 0 0). The tendencies of the film formation process and the interdiffusion at the interface were similar in both the (1 1 1) and (1 0 0) cases. However, the strain at the interface of films on the (1 0 0) substrate was larger than that on the (1 1 1) substrate. In the case of (1 1 1), lattice relaxation is found at the interface and the strain distribution of Ni layers is not uniform over the plane. From the observation of the traces of the atoms in early stage of film formation, it was found that the range of migration of adatoms on (1 1 1) surface is longer than that on (1 0 0) and the Ni nuclei as large as three atoms are mobile on Pd (1 1 1) surface.

Production Cross Sections of Fragments from Beams of 400–650 MeV per Nucleon9Be,11B,12C,14N,15N,16O,20Ne,22Ne,56Fe, and58Ni Nuclei Interacting in a Liquid Hydrogen Target. II. Isotopic Cross Sections of Fragments

We have measured the isotopic cross sections of 130 secondary fragmentation isotopes from 10 different beam nuclei from 9Be to 58Ni that were accelerated to between 400 and 650 MeV nucleon-1 at the SATURNE Accelerator in France in 1993 and 1994. These beam nuclei interacted in a 1.52 g cm-2 thick liquid hydrogen target, and the isotopic fragments were observed. This is the first use of a pure hydrogen target with a thickness approximating the amount of hydrogen traversed by cosmic rays in our Galaxy to measure cross sections. Several of the beam charges such as 9Be,11B,15N, and 22Ne have not had their fragmentation cross sections measured previously. The isotopic cross sections from the 12C,14N,16O,20Ne,56Fe, and 58Ni beam interactions are compared with earlier measurements by our group using a CH2 - C target subtraction technique to determine the hydrogen cross sections. The overall agreement between the new measurements and the earlier measurements using a CH2 - C target subtraction is excellent with a systematic consistency between measurements ~3%-5%. These new isotopic cross sections define the Galactic production of the secondary isotopes 10Be,10B,11B,13C,14N,15N, and 18O as well as Fe and Ni secondary decay isotopes from Cl to Co to a level of precision of ~3%-5%. These cosmic-ray isotopes are important for understanding the nucleosynthesis in the cosmic-ray sources as well as tracing the detailed propagation history of cosmic rays in the Galaxy.

In situ EXAFS study of the nucleation and crystal growth of Ni particles on SiO 2 support

Ni/SiO 2 catalysts were prepared by wetness impregnation method (INi) and by a new two-step method (ENien 2.5/600+INi 2.5). The two-step method consists of formation of chemical glue, “nickel nuclei”, having strong metal support interaction with SiO 2 and preparation of the “nickel reservoir” which has weak interaction with support. The nucleation and growth behaviors of such Ni/SiO 2 catalysts in the preparation stage were continuously monitored by in situ EXAFS spectroscopy. The in situ EXAFS spectra of INi catalyst began to change after 320°C and bulk NiO like structure was formed at 500°C heat treatment. The Ni/SiO 2 prepared with the two-step method had larger coordination number of Ni with silica support in the initial stage of in situ monitoring than that of INi catalyst, which showed the coexistence of Ni nuclei and Ni reservoir. The ENien 2.5/600+INi 2.5 had smaller particles of Ni compared with INi after high temperature calcination. The formation of small Ni particles could be attributed to the strong ion-support interaction of nickel nuclei with nickel reservoir in ENien 2.5/600+INi 2.5 catalyst. Slight particle growth occurred after 370°C calcination in Ni/SiO 2 prepared by two-step method.

Nuclear Processes in Hydrogen-Loaded Metals

Miley et al. and, independently, Mizuno et al. claim to have observed nuclides produced in Ni (Z = 28) when an electrolytic light-water cell is used. Miley et al. use thin layers of Ni (≤5 × 10-6 cm) and claim that the effect is reproducible. The secondary nuclides are distributed in a wide range of Z and A and show nuclides with Z < 28 and accumulations at Z = 48 and 78. If the nuclides at Z = 48 and 78 are Ni-Ni fusion, they can be produced only when the original Ni nuclei gain sufficient kinetic energy to overcome the Ni-Ni repulsive Coulomb barrier.The foregoing data are discussed in terms of current physics. In particular, it is assumed that the gain of kinetic energy derives from an impulsive increase of absolute nuclear binding energies of Ni due to a high rate of capture of orbital electrons and consequent almost instantaneous multiple p → n transitions. Under this hypothesis, neutrino emission should be detected during nuclear transmutation.

Beta-decay of 56Cu

By measuring positrons and β-delayed γ-rays emitted from mass-separated sources, the decay of 56Cu (4 +, T z =−1, T=1) to states in the doubly-magic nucleus 56Ni was studied for the first time. The half-life of 56Cu was measured to be 78(15) ms, and four β-delayed γ-rays were assigned to its decay. The resulting experimental data on Fermi and Gamow–Teller strength are compared with shell-model predictions.

Study of initial layer formation of Zn–Ni alloy electrodeposition by in situ ellipsometry

Initial layers of Zn, Ni, and Zn–Ni alloy electrodeposition on Au electrode in sulfate baths are detected in a nm thickness range by in situ ellipsometry. The thin layer deposits are also analyzed by Auger electron spectroscopy (AES), and ICP atomic emission spectroscopy. The preferential deposition of Zn, in the initial thin layer of Zn–Ni alloy deposition, is confirmed by the analysis. From the ellipsometric measurements, the underpotential deposition (UPD) of Zn is observed; i.e. the Zn deposition starts at a potential more positive by 0.5 V than the redox potential of Zn 2+ /Zn, while noticeable UPD of Ni cannot be observed. For Zn–Ni alloy deposition, the thin layer of Zn formed in the UPD potential region greatly inhibits the Ni deposition. It is speculated that the preferential Zn deposition in Zn–Ni alloy electroplating is caused by the inhibition of Ni nuclei growth due to a thin layer of Zn on the deposited Zn–Ni alloy.

Study of the56Ni(d,p)57NiReaction and the Astrophysical56Ni(p,γ)57CuReaction Rate

The single-particle character of states outside the doubly magic (radioactive) nucleus 56Ni has been determined through a measurement of the (d,p) neutron transfer reaction using inverse kinematics. From the spectroscopic factors of the low-lying states in 57Ni, the astrophysically interesting yield for the 56Ni(p,γ) reaction to the mirror nucleus 57Cu has been calculated, utilizing charge symmetry. The rate for this reaction in the temperature range typical of novae, supernovae, and x-ray bursts is found to be more than 10 times higher than previously assumed.Received 29 August 1997DOI:https://doi.org/10.1103/PhysRevLett.80.676©1998 American Physical Society

In situSTM study of the electrodeposition and anodic dissolution of ultrathin epitaxial Ni films on Au(111)

A detailed in situ STM study of the electrodeposition and electrochemical dissolution of Ni on reconstructed Au(111) electrode surfaces in various electrolytes is presented, demonstrating the electrochemical formation of well-defined, ultrathin, epitaxial Ni films. Formation of Ni nuclei starts below the ${\mathrm{Ni}}^{0}{/\mathrm{N}\mathrm{i}}^{2+}$ Nernst potential via place exchange of Ni with Au atoms at the elbows of the herringbone reconstruction, followed by nucleation of Ni islands on top of these substitutional Ni atoms at overvoltages $\ensuremath{\eta}&gt;~80\mathrm{mV},$ and by nucleation at step edges of the Au substrate at $\ensuremath{\eta}&gt;~100\mathrm{mV}.$ At submonolayer coverages islands with two different growth morphologies, compact, triangularly shaped and highly anisotropic, needlelike islands, are observed. Upon further growth these islands coalesce and an almost perfect two-dimensional Ni monolayer is formed. Multilayer growth was studied up to coverages of 5 ML; it exhibits a similar layer-by-layer growth, resulting in very smooth Ni films. In atomic-scale observations a hexagonal Ni lattice with a lattice spacing of 2.5 \AA{} is resolved, similar to the (111) orientation in bulk Ni, and with the same orientation as the Au lattice. The order in the highly defective first Ni layer is considerably improved by second-layer deposition. The significant differences to vapor-deposited Ni on Au(111) indicate a structure-decisive role of coadsorbates in the electrochemical environment. Dissolution of the Ni films at potentials positive of the Nernst potential proceeds via formation of etch pits and step-flow etching.

VoyagerMeasurements of the Mass Composition of Cosmic‐Ray Ca through Fe Nuclei

We present measurements of the charge and isotopic composition of cosmic-ray Ca through Fe nuclei made on the Voyager spacecraft. We have analyzed 18 years of data in the energy range 100-300 MeV nucleon-1 collected by the High Energy Telescope of the cosmic-ray subsystem experiment on the Voyager 1 and 2 spacecraft. The average solar modulation level for this measurement is 480 MV. These data have several times the statistical accuracy and have mass resolution comparable to the best previously published measurements covering this charge range from the ISEE cosmic-ray experiment. Many of the isotopes of these charges are dominated by secondary production from cosmic rays traversing the interstellar medium, and for these isotopes our measured isotopic fractions are generally consistent to within 10%, with the exception of certain K-capture isotopes, with those calculated for secondary production using the latest propagation codes and cross sections. For five isotopes,40Ca,52Cr,55Mn,54Fe, and 58Fe, we can determine the cosmic-ray source composition to an improved accuracy over previous values. None of these isotopes show any significant differences with respect to the solar composition. This result, taken with other recent Voyager measurements of the isotopic composition of charge Z = 6-16 nuclei as well as Co and Ni nuclei, now provide the source composition of ~20 individual cosmic-ray isotopes with Z between 6 and 28 measured by the same instrument under the same conditions. This source composition is remarkably solar-like with only 13C,14N, and 22Ne isotopes showing significant abundance differences. This degree of similarity is not well explained by present specific models for the cosmic-ray origin and is discussed further in this paper.

Structure of odd-odd Cu isotopes in the framework of the interacting boson-fermion-fermion model

In the present work, odd-odd ${}^{62,64,66}$Cu nuclei have been studied in the framework of the interacting boson-fermion-fermion model (IBFFM). Odd-odd Cu nuclei have been described with the parameters obtained from the IBM calculation for even Ni nuclei and the IBFM description of odd mass Cu and Ni nuclei. A simple delta interaction has been assumed between the odd neutron and the odd proton in the odd-odd nuclei. The calculated excitation energy values and the magnetic moments of odd Cu and Ni nuclei in the IBFM are compared to show the effectiveness of the parameters in explaining the low energy structure of these nuclei. Excitation energy spectra, magnetic moment and spectroscopic factors for the single-nucleon transfer reaction have been calculated for the odd-odd nuclei and are compared with the corresponding experimental values. The results seem to indicate the ability of the model to explain the low energy structure of odd-odd Cu nuclei.

Voyager measurements of the isotopic composition of Fe, Co and Ni nuclei—Implications for the nucleosynthesis and the acceleration of cosmic rays

We report new measurements of the cosmic-ray elemental and isotopic composition of Fe, Co and Ni nuclei in the energy range from 110 to 298 MeV per nucleon. These measurements were made using the High Energy Telescope of the CRS experiment on the Voyager 1 and 2 spacecraft during the time period from 1977 to 1996. In this overall time period of 18 years the average solar modulation parameter Φ was about 480 MV. On the basis of the 2710 Fe events, 16 Co events and 135 Ni events observed we find that the isotopic composition for Fe, Co and Ni is consistent with a solar-like source composition. The isotopic composition of Co indicates that the time delay between nucleosynthesis and cosmic-ray acceleration is probably larger than a few x 10 4 yr.