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

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

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

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

Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment

In the PS209 experiments at CERN two kinds of measurements were performed: the in-beam measurement of X-rays from antiprotonic atoms and the radiochemical, off-line determination of the yield of annihilation products with mass number A_t -1 (less by 1 than the target mass). Both methods give observables which allows to study the peripheral matter density composition and distribution.Comment: LaTeX (espcrc1 style), 6 pages, 3 EPS figures, 1 table, Proceedings of the Sixth Biennal Conference on Low-Energy Antiproton Physics LEAP 2000, Venice, Ital

Cross Sections, Recoil Ranges, and Angular Distributions of Nuclei Produced in 20-200 MeV Alpha Bombardment of 59-Co

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit