Accession Number : AD0651111

Title :   NEUTRON SPECTRA FROM MONOENERGETIC PHOTONS ON BISMUTH.

Descriptive Note : Doctoral thesis,

Corporate Author : ILLINOIS UNIV URBANA DEPT OF PHYSICS

Personal Author(s) : Hanson,A. O. ; Sutton,D. C.

Report Date : 1967

Pagination or Media Count : 50

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)

Descriptors :   (*BISMUTH, *PHOTONUCLEAR REACTIONS), (*NEUTRONS, *NUCLEAR RADIATION SPECTROSCOPY), BREMSSTRAHLUNG, PHOTONS, GAMMA NEUTRON REACTIONS, NUCLEAR RESONANCE, ELECTRIC MOMENTS, FAST NEUTRONS, THERMAL NEUTRONS, GROUND STATE, NUCLEAR ENERGY LEVELS, DIPOLE MOMENTS

Subject Categories : Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE