NEUTRON SPECTRA FROM MONOENERGETIC PHOTONS ON BISMUTH.
Abstract
Spectra of photoneutrons from a Bi209 target were obtained in the electric dipole giant resonance region (12 MeV - 16 MeV). Gamma-ray energy resolution of 1.5% was attained using a bremsstrahlung monochromator; the neutron energies were measured with a time-of-flight technique with resolution which varied from 10% at 2 MeV to 15% at 6 MeV. About 88% of the neutrons emitted by 14-MeV gamma rays are statistical. The inferred level density of Bi208 near its ground state is not a simple function of excitation energy, but from 4 to 7 MeV it increases exponentially with energy; in that energy range the temperature is about 1 MeV. The non-statistical high-energy neutrons leave the Bi208 nucleus at the excitation energies at which the states are well represented as single-neutron holes in Bi209. These high-energy neutrons are intimately connected with the giant resonance. If the giant resonance is dominated by a single dipole state, the absolute width which characterizes the decay of the dipole state into the compound nucleus must increase by a factor of about 3 between 12 and 16 MeV. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1967
- Accession Number
- AD0651111
Entities
People
- A. O. Hanson
- D. C. Sutton
Organizations
- University of Illinois Urbana–Champaign