Ni Nuclei Research Articles

Cumulative particle production on proton and nucleus beams

The experimental results from a systematic study of cumulative π ± , K ± , p, and d production in the inclusive process B+A→c+X are presented. The beam B was protons, deuterons, helium nuclei, or carbon nuclei with momentum per nucleon equal to 4.5 GeV/ c. The A dependence of the cross sections was measured for these beams for fixed secondary-particle momentum equal to 0.5 GeV/ c and emission angle ϑ=120°. The fragmenting nuclei are D, He, 6 Li, 7 Li, C, Al, Si, Cu, 58 Ni, 64 Ni, 64 Zn, 114 Sn, 124 Sn, and Pb. The energy dependence of the π ± -meson, proton, and deuteron cross sections in the momentum range 0.3–0.7 GeV/ c (ϑ=120°) was measured for 58 Ni, 64 Ni, 64 Zn, 114 Sn, 124 Sn, and Pb nuclei using an 8.9 GeV/ c proton beam. Details of the behavior of the cross sections were found in various nuclear fragmentation regions. The behavior of the exponent of the A dependence of the proton, deuteron, and pion cross sections as a function of the mass number of the nuclei in the primary beam was studied. The results are compared with the data available in the literature. Various models of cumulative particle production in interactions of hadrons and nuclei with nuclei at various beam energies are discussed. Tables of invariant differential cross sections are presented, along with the results of fitting the energy dependence of the cross sections in various representations.

High spin spectroscopy of exotic nuclei

The present status and future development of experimental techniques and approach to 100Sn in in-beam spectroscopy are reviewed. The structure information obtained from recent studies of the T x =1 nuclei 94Pd, 98Cd and 102Sn is discussed with respect to shell structure, increasing proton-neutron interaction and excitations of the N=Z=50 doubly magic core. First results from neutron rich Ni nuclei and their shell model analysis are presented.

Nucleation and growth of Ni-LIGA layers

The quality of a Ni-LIGA layer and its adhesion to TiO2 depend crucially on interface morphology and chemistry. The unique combination of ARXPS (angle resolved photo electron spectroscopy), STM (Scanning tunnel microscopy) and DTS (distance tunnel spectroscopy) yield new insights in morphology and stoichiometry on the porous TiO2 plating ground, on the TiO 2-x (OH) y NiO z Ni interface, and on the Ni-nucleation and growth. Aside TiO2-pore dimension, we identified graphite hillocks, with retarded Ni coverage, the adhesion promoting interface oxide TiO 2-x (OH) y Ni z and the Ni nuclei and their expansion.

Immunocytochemical and histochemical analyses of gonadotrophin releasing hormone, tyrosine hydroxylase, and cytochrome oxidase reactivity within the hypothalamus of chicks showing early sexual maturation

In order to determine the changes in gonadotrophin releasing hormone (GnRH) and dopaminergic activity within the brain during the onset of sexual precocity, a Halasz-like knife was developed to produce discrete parasagittal cuts in 2-week-old male broiler chicks. At 5 weeks of age, sexually precocious respondents were selected on the basis of advanced secondary sex characteristics and randomly paired with sham-operated controls. Each pair of birds was perfused with heparinized saline followed by 4% paraformaldehyde. Sections 40 microns thick, obtained throughout the hypothalamus, were immunostained with either anti-GnRH or anti-tyrosine hydroxylase (TH) to ascertain dopaminergic activity. Alternate sections from each pair of brains were also treated with cytochrome oxidase to determine metabolic activity levels or with Nissl stain to localize the knife cuts. Analysis revealed an increase in GnRH immunoreactivity within the bed nucleus of the pallial commissure (nCPa) and paraventricular nucleus (PVN), as well as the median eminence (ME). An increase in TH immunoreactivity was observed in the nucleus intramedialis (nI). Also an increase in metabolic activity was seen in the PVN as revealed by cytochrome oxidase reactivity. It is hypothesized that during the onset of puberty there is an increase in immunoreactive GnRH cell numbers as a result of a decrease in the inhibition of the GnRH system, possibly involving the nI and PVN. The source of the dopamine reported in the ME could be from the nI and other nearby nuclei. Dopamine from the tubero-infundibular area may be one of the putative neurotransmitters responsible for the increased activity of GnRH within the ME of chicks showing precocious puberty.

TREK: A cosmic-ray experiment on the Russian space station MIR

The goals of the TREK experiment, now in place on the MIR Space Station, are to resolve and measure the composition of both odd-Z and even-Z cosmic-ray nuclei up to uranium, to measure the isotopic composition of Fe-group nuclei, and to search for transuranic nucleic and exotic particles such as strangelets. To collect tracks of ultraheavy cosmic rays, exterior panels holding an array of BP-1 phosphate glass 1.2m2 in area and 16 plates thick are now mounted outside the Kvant-2 module on MIR. Heaters and relays regulate the temperature of the glass at 25°±5°C. The detectors will record ∼103 cosmic-ray tracks withZ≥50 during ∼2.5 years. An interior panel consisting of an array 0.09 m2 in area and 32 plates thick and mounted on the inside wall of the Soyuz spacecraft (attached to the Space Station) will collect tracks of about 13000 Fe and 500 Ni nuclei.

Relativistic mean field study of light medium nuclei away from beta stability.

Bulk properties like binding energies, rms radii, and quadrupole deformations of Ca, Ti, Cr, Fe, Ni, and Zn nuclei are calculated in the deformed relativistic mean field model. Excellent results for the experimentally known binding energies and radii of nuclei are obtained. The calculation is extended to nuclei near the neutron-drip line. Dips in quadrupole deformation are seen for the known closed-shell configurations and enhanced deformations are obtained for specific neutron numbers.

Magnetic hyperfine interaction studies of isolated Ni impurities in Pd and Pd-Pt alloys.

The magnetic hyperfine fields at isolated Ni impurities in Pd and Pd-Pt alloys were studied with the perturbed-angular-distribution (PAD) method by measuring the temperature, magnetic field, and concentration dependence of the nuclear-spin Larmor precession of isomeric states in $^{63}\mathrm{Ni}$. The recoil-implanted Ni nuclei, as products of heavy-ion nuclear reactions, are present in extreme dilution (<1 ppm) in the hosts. The positive Larmor frequency shift (Knight shift) observed for Ni impurities in Pd follows a Curie-Weiss-like temperature dependence with a large Curie constant indicating a giant moment behavior. For Ni impurities in the Pd-Pt alloys a considerable positive shift remains even at 30 at. % Pt content. The variation of the shift with Pt concentration and temperature reflects the variation of the Pd-Pt alloy susceptibility. The different contributions to the hyperfine field could be differentiated by comparing the Knight shift for Ni in Pd with its susceptibility contribution obtained from extrapolated susceptibility measurements in dilute Pd-Ni alloys. The negative core-polarization field of the impurity spin moment is compensated for by a transferred hyperfine field correlated with the host polarization in the neighborhood of the impurity. The remaining positive hyperfine field is due to a weak orbital moment of 0.3${\ensuremath{\mu}}_{B}$ at the impurity site. The values obtained for the different contributions are compared with results of the Korringa-Kohn-Rostoker--coherent-potential-approximation calculations for concentrated Pd-Ni alloys extrapolated to the dilute limit.

Alpha-particle scattering from Ni isotopes at 25 MeV

Differential cross sections have been measured for both elastic and inelastic scattering of 25 MeV alpha particles from 58,60,62,64Ni nuclei. An increasing neutron skin thickness in the isotopic sequence from 58Ni to 64Ni has been found. The angular distributions of excited states have been analysed by the coupled-channel (CC) approximation, in the context of the vibrational model. The analysis reveals enhanced hexadecapole (0+ to 4+) transitions in 58,60,64Ni. Deformation parameters for the excited states have been deduced. Isoscalar transition rates have been extracted and compared with electromagnetic transition rates.

61Ni Mössbauer spectra of fine Ni particles

We report the first measurements of fine Ni particles from61Ni Mossbauer spectroscopy. The average hyperfine field of the 10 nm particles at 4.2K is measured to be 7.7(4) T, compared to the measured value for Ni foil of 7.5(3) T. Application of an external field of 6 T to the fine particles causes a reduction of the hyperfine splitting to 1.5(6) T, a consequence of the negative hyperfine field at Ni nuclei. These results are discussed in terms of fine particle effects.

A-particle scattering from Ni isotopes at Eα = 172.5 MeV

Differential cross sections have been measured for the elastic and inelastic scattering of 172.5 MeV α-particles from 58,60,62,64Ni nuclei. The analysis of the experimental data of elastic scattering in terms of optical potentials indicates an increasing neutron skin thickness in the isotopic sequence from 58Ni to 64Ni. Coupled-channel analyses based on the anharmonic vibrational model approach determine the values of the dynamic deformation parameters for the most strongly excited states rather precisely and reveal enhanced hexadecapole (0 + → 4 + 1) transitions. Using an implicit folding-model procedure with a correction for the density dependence of the effective α N interaction, isoscalar transition rates are extracted and compared to electromagnetic results.

Collective bands in81Sr

Deformed Hartree-Fock calculations are carried out for 81Sr in the 2p3/2, 2p1/2, 1f5/2 and 1g9/2 valence space with the nucleus 56Ni as the core. Kuo's (1969) effective interaction and an interaction obtained from it by modification of some of the matrix elements are used. Bands of states of definite angular momenta projected from highly deformed intrinsic states with K=5/2- and 1/2- are obtained. The calculated energy spectra and the B(E2) values for transitions within the bands are in fair agreement with the experimental ones. A positive parity band with K=5/2+ and a small deformation has spectral features similar to those observed for the band having the J=7/2+ state as the band head. Finally an alternative suggestion is made for the possible structure of the observed K=1/2+ band with a large deformation.

TDHF studies of heavy-ion collisions leading to the compound nucleus56Ni

The time-dependent Hartree-Fock approach is applied to the study of entrance-channel effects in heavy-ion collisions leading to the formation of the compound nucleus 56Ni. The systems 16O+40Ca, 17O+39Ca, 20Ne+36Ar, 24Mg+32S and 28Si+28Si are investigated for various laboratory energies at and above the Coulomb barrier. In the TDHF calculations the authors employ the separable frozen wavefunction approximation. The fusion results are qualitatively similar for all the systems but there are significant quantitative differences in the mass and charge transfer characteristics which reflect the importance of the entrance channel.

Stability and reactivity of (001) and (111) NiO: a RHEED-AES investigation of Si surface segregation and Ni formation by gas reduction

Abstract In this contribution are reported recent results regarding the preparation and the reactivity of different nickel oxide (NiO) monocrystalline surfaces. At first, it concerns a structural investigation of metal formation by hydrogen reduction of (001) NiO. In most cases, Ni nuclei form three-dimensional islands as observed by RHEED and corroborated by AES. At low temperatures, metal stacking, previously described as pure hcp stacking from (1120) planes, is shown to develop, in reality, with stacking faults from which fcc stacking is often formed. At high temperatures, metal stacking is retained as within the oxide and, from a comparative transmission electron microscopy investigation, a model for the topotactic nucleus formation is put forward. Secondly, the preparation and the stability of (111) NiO are investigated. Apparent (111) NiO stability is found to be due to the thermal surface segregation of silicon. Even in very low amount, this very mobile impurity segregates at the (111) NiO surface leading to a two-dimensional O-Si-Ni compound.

Stability and reactivity of (001) and (111) NiO: A RHEED-AES investigation of Si surface segregation and Ni formation by gas reduction

In this contribution are reported recent results regarding the preparation and the reactivity of different nickel oxide (NiO) monocrystalline surfaces. At first, it concerns a structural investigation of metal formation by hydrogen reduction of (001) NiO. In most cases, Ni nuclei form three-dimensional islands as observed by RHEED and corroborated by AES. At low temperatures, metal stacking, previously described as pure hcp stacking from (112̄0) planes, is shown to develop, in reality, with stacking faults from which fcc stacking is often formed. At high temperatures, metal stacking is retained as within the oxide and, from a comparative transmission electron microscopy investigation, a model for the topotactic nucleus formation is put forward. Secondly, the preparation and the stability of (111) NiO are investigated. Apparent (111) NiO stability is found to be due to the thermal surface segregation of silicon. Even in very low amount, this very mobile impurity segregates at the (111) NiO surface leading to a two-dimensional O-Si-Ni compound.

Electronic Structure Ni–Pd Alloys Calculated by the Self-Consistent KKR-CPA Method

The electronic structure of disordered Ni–Pd alloys is investigated by means of the KKR method which is combined with the CPA and the local-spin-density approximation. Good overall agreements with the measurements are obtained for the magnetic moment distribution and for the hyperfine field at Ni nucleus. The origins of the large magnetic moment at Ni site (∼1.2 µ B ) and the positive hyperfine field on the Ni nucleus, both in Pd-rich region, are discussed in the light of the present calculation which can reproduce them quantitatively.

Nuclear fragmentation with 100 MeV ?-particles

Reaction products from the collision of 100 MeVα-particles with Ca and Ni nuclei have been investigated at the Julich cyclotron. Energy spectra and angular distributions of fragment isotopes with 1≦A≦12 have been measured. The data differ from standard compound or precompound nuclear model expectations and are rather similar to high energy heavy ion data. A simple analysis using the coalescence model and the geometrical concept of the fireball model describes the essential features of the data surprisingly well.

Elastic scattering of 9Be on heavy target nuclei

The elastic scattering of 9Be ions on Mg, Al, Si, Ca, Ni, Ag and Au target nuclei has been studied at 14, 20 and 26 MeV projectile energy. Excitation curves on Si were measured at four angles in the energy range of 14–20 MeV. A universal optical potential fitting all these angular distributions was found and ambiguities of the parameters are discussed. For each target the interaction distance, the strong absorption distance and the sensitive regions were calculated.

The effects of drugs on the field potential in the caudate nucleus following nigra stimulation.

The reciprocal connections of the caudate (Cd) and nigra (Ni) nuclei have been extensively studied using anatomical 2, 17, 26, 27, 28, 35, 36, 37, histochemical 1, 13, 30, 8 and electrophysiological 3, 6, 9, 12, 14, 15, 22, 23, 24. 38 methods but in some respects the situation is even less satisfactory than a few years ago. The present communication is aimed at examining the characteristics of field potentials in the Cd evoked from stimulation of the Ni before and after systemic application of drugs. The cats were anaesthetized with sodium pentobarbital (30–40 mg/kg), immobilized by flaxedil and artifically ventilated. The overlying cortical structures were removed by suction to expose the dorsal surface of the Cd. The nigro-caudate pathway was electrically stimulated using bipolar electrodes placed in the Ni proper. Similar electrodes in the cerebral peduncle (CP) allowed antidromic activation of the Cd. Field potentials were recorded in the medial two thirds of the ipsilateral Cd with glass microelectrodes filled with either 2 M sodium chloride or 3 M potassium chloride (DC resistance: 3–5 MΩ). A Nicollete 1074 was used for averaging the signals. The recording and stimulating electrode tracts were identified histologically.KeywordsSubstantia NigraField PotentialCaudate NucleusCorpus StriatumPositive WaveThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Global Viewpoint on Nuclear-Particle-Emission Cross Sections at Intermediate Energies

It follows from the independent-particle picture of the nucleus that the cross section for the reaction (d, /sup 6/Li) depends upon the target mass number A as approx. A/sup -3/./sup 33/, this result indicates the significance of a recent empirical observation. The energy-integrated cross sections for emission of p, d, /sup 3/H, /sup 3/He, and /sup 4/He from Mg, Ni, and Ag nuclei bombarded by a 235-MeV pion beam show some features suggestive of nuclear structure. (AIP)

On the structure of low-lying levels in 56Ni

It is shown possible to understand the structure of the low-lying states in the nucleus 56Ni, in a simple way, in terms of the Hartree-Fock intrinsic states resulting from the Kuo-Brown effective interaction for the 2p-1f shell, modified slightly so as to satisfy certain constraints imposed on it by the B( E2) (0 → 2) systematics in the shell.