Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Energy-averaged neutron total cross sections of cobalt were measured from approx. =0.5 to 12.0 MeV. Differential elastic- and inelastic-scattering cross sections were measured from approx. =1.5 to 10.0 MeV over the scattering-angle range approx. =18° to 160°, with sufficient detail to define the energy-averaged behavior. Inelastic neutron groups were observed corresponding to ''levels'' at: 1115 +- 29, 1212 +- 24, 1307 +- 24, 1503 +- 33, 1778 +- 40, 2112 +- 40, 2224 +- 35, 2423 +- 39, 2593 +- 41 and 2810 keV. The experimental results were interpreted in terms of the spherical optical-statistical and coupled-channels models. An unusually successful description of observables was achieved over a wide energy range (-15.0 to 20.0 MeV) with a spherical model having energy-dependent strengths and geometries. The energy dependencies are large below approx. =7.0 MeV (i.e., approx. =19.0 MeV above the Fermi energy), but become smaller and similar to those reported for ''global'' potentials at higher energies. The imaginary strength is large and decreases with energy. These imaginary-potential characteristics are attributed to neutron shell closure and collective-vibrational processes. The weak-coupling model also offers an explanation of the unusual negative energy slope and relatively small radius of the imaginary potential. The spherical optical model derived from the neutron-scattering results was extrapolated to bound energies using the dispersion relationship and the method of moments. The resulting real-potential strength and radius peak at approx. =-10.0 MeV, while concurrently the real diffuseness is at a minimum. The extrapolated potential is approx. =8% larger than that implied by reported particle-state energies, and approx. =13% smaller than indicated by hole-state energies. 68 refs., 15 figs., 1 tab.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Differential elastic- and inelastic-scattering cross sections, measured from approx. 1.5 to 10.0 MeV, are interpreted in terms of spherical-optical-statistical (OM) and coupled-channels models. A successful description of the differential elastic scattering below 10 MeV and the total cross section to 20.0 MeV is achieved using the spherical OM with energy-dependent strengths and geometries. These energy dependencies are large below approx. 7.0 MeV, but become smaller and similar to those reported for /open quotes/global/close quotes/ potentials at higher energies. This change in the energy dependence of the parameters probably marks the onset of the Fermi surface anomaly approx. 19 MeV above the Fermi energy. Inelastic scattering to the levels below 1.8 MeV displays a forward-peaked behavior. This nonstatistical component is interpreted using the weak-coupling model in which the f--2 proton hole is coupled to the 2/sup /plus// state in 6°Ni. This model provides an explanation of the unusual energy dependence and relatively small radius found for the imaginary OM potential. The coupling also contributes to the large value of this potential. The real spherical OM potential derived from the neutron-scattering results is extrapolated to bound energies by using the dispersion relationship and the method of moments. The resulting real-potential strength and radius peak at approx.-10.0 MeV, whereas the real diffuseness is at a minimum at this energy. The extrapolated potential is approx. 8% larger than that implied by reported particle-state energies, and approx. 13% smaller than indicated by hole-state energies. 42 refs., 8 figs.
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Author: Dennis Charles Healey
Author: Joseph M. Harrer
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Author: Smithsonian Science Information Exchange
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