504 research outputs found
Present status of GaAs
An extensive literature survey on GaAs was carried out for the period December 31, 1970, to December 31, 1977. The increasing interest in GaAs device structures increased steadily during that period. The leading research and development centers and the specific areas of interest were identified. A workshop on GaAs was held in November 1977 to assess the present status of melt-grown GaAs and the existing needs for reliable chemical, structural, and electronic characterization methods. It was concluded that the present available bulk GaAs crystals are of poor quality and that GaAs technology is lagging demonstrated or potentially feasible GaAs devices and systems
Model Calculations of the Nucleon Removal by 80-164 MeV Protons from Medium-Mass Nuclei
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
Recoil Ranges of Nuclei Produced in Proton-Induced Reactions
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
Composition of the nuclear periphery from antiproton absorption
Thirteen targets with mass numbers from 58 to 238 were irradiated with the
antiproton beam from the Low Energy Antiproton Ring facility at CERN leading to
the formation of antiprotonic atoms of these heavy elements. The antiproton
capture at the end of an atomic cascade results in the production of more or
less excited residual nuclei. The targets were selected with the criterion that
both reaction products with one nucleon less than the proton and neutron number
of the target be radioactive. The yield of these radioactive products after
stopped-antiproton annihilation was determined using gamma-ray spectroscopy
techniques. This yield is related to the proton and neutron density in the
target nucleus at a radial distance corresponding to the antiproton
annihilation site. The experimental data clearly indicate the existence of a
neutron-rich nuclear periphery, a "neutron halo", strongly correlated with the
target neutron separation energy Bn and observed for targets with Bn < 10 MeV.
For two-target nuclei 106Cd and 144Sm, with larger neutron binding energies, a
proton-rich nuclear periphery was observed. Most of the experimental data are
in reasonable agreement with calculations based on current antiproton-nucleus
and pion-nucleus interaction potentials and on nuclear densities deduced with
the help of the Hartree-Fock-Bogoliubov approach. This approach was, however,
unable to account for the 106Cd and 144Sm results.Comment: Latex (RevTeX,aps style), 13 pages + 12 Postscript figure
Hybrid-Model Calculations of the Nucleon Removal by 80-164 MeV Protons from Medium-Mass Nuclei
This work was supported by National Science Foundation Grant PHY 75-00289 and Indiana Universit
Linear Momentum Transfer in the 3-He + 59-Co Reaction at Energies Between 110 and 170 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Gold fragmentation induced by stopped antiprotons
A natural gold target was irradiated with the antiproton beam from the Low
Energy Antiproton Ring at CERN. Antiprotons of 200 MeV/c momentum were stopped
in a thick target, products of their annihilations on Au nuclei were detected
using the off-line gamma-ray spectroscopy method. In total, yields for 114
residual nuclei were determined, providing a data set to deduce the complete
mass and charge distribution of all products with A > 20 from a fitting
procedure. The contribution of evaporation and fission decay modes to the total
reaction cross section as well as the mean mass loss were estimated. The
fission probability for Au absorbing antiprotons at rest was determined to be
equal to (3.8+-0.5)%, in good agreement with an estimation derived using other
techniques. The mass-charge yield distribution was compared with the results
obtained for proton and pion induced gold fragmentation. On the average, the
energy released in pbar annihilation is similar to that introduced by ~ 1 GeV
protons. However, compared to proton bombardment products, the yield
distribution of antiproton absorption residues in the N-Z plane is clearly
distinct. The data for antiprotons exhibit also a substantial influence of
odd-even and shell effects.Comment: 14 pages, 9 figures, Revtex 4, to be published in Physical Review
LES NOYAUX DE TRANSITION 189Ir ET 187Ir SONT-ILS TRIAXIAUX ?
Les niveaux excités des noyaux 189Ir et 187Ir ont été étudiés par réaction (α, 2nγ) sur le faisceau du cyclotron de Grenoble. Les schémas détaillés qui ont été établis mettent en évidence : 1) des états de parité positive qui s'interprètent comme appartenant aux deux bandes 3/2+ | 402 | (fondamental) et 1/2+ | 400 | mélangées par interaction de Coriolis (noyaux a symétrie axiale de déformation positive) ; 2) une bande découplée construite sur un état 9/2- (h 9/2) décrite de manière équivalente par un modèle à symétrie axiale et déformation positive ou par un modèle a particule-plus-rotor asymétrique ; 3) une structure complexe pour les niveaux de parité négative associés à l'isomère 11/2- (h 11/2). Ce système est correctement prédit par le modèle à rotor asymétrique
Multiplicity of Gamma-Ray Transitions Observed in Lithium-Induced Reactions
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
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