Near threshold coincident electrofission of uranium-238

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5227913

Dowell, D H

Using the 100% duty cycle electron beam from the University of Illinois MUSL-2 accelerator, inelastic electron scattering form factors have been measured in coincidence with the fission decay of /sup 238/U. Data was taken at effective elastic momentum transfers of .36, .41, .45 and .59 fm-/sup 1/ and electron-fission fragment angular correlations were measured perpendicular to and along the momentum transfer axis. The beam energies used were 67.11, 56.91 and 46.49 MeV, with the outgoing electron detected at 60/sup 0/ and 80/sup 0/, relative to the beam direction. The electron energy resolution was .1% and the form factors were measured for excitation energies from 2 to 12 MeV. A prominent, anisotropic threshold peak is seen in the coincident form factors. An analysis of the q-dependence of the data and of the angular correlation indicates the observed strength is E2. Fission threshold for this E2 strength is about 5.7 MeV as compared with 6 MeV for E1 decays. The peak itself is due to the onset of neutron competition at 6.15 MeV. The threshold region, when analyzed using a Gaussian K-distribution to describe the statistical density of K-states near the fission barrier, exhibits a step-like change in the value of K/sub 0//sup 2/ at .7 MeV above the threshold. This indicates a possible energy gap in the E2 transition states. The decay is isotropic above 7.5 MeV excitation energy. From 7 to 11.7 MeV, the distribution of E2/E0 strength is relatively flat with the total strength in this region exhausting approximately 10% of an energy weighted sum rule. A comparison with hadron scattering experiments suggests that some of the strength near 11.5 MeV is due to the fission decay of the giant monopole resonance with a fission probability similar to that of E2 transitions.

• Research Organization: Illinois Univ., Urbana (USA)
• OSTI ID: 5227913
• Country of Publication: United States
• Language: English

Related Subjects

651925 -- Nuclear Properties & Reactions
A=190-219
Experimental-- Nuclear Reactions & Scattering-- (-1987)
651926* -- Nuclear Properties & Reactions
A=190-219
Experimental-- Spontaneous & Induced Fission-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
ANGULAR DISTRIBUTION
CHARGED-PARTICLE REACTIONS
DATA
DISTRIBUTION
E1-TRANSITIONS
E2-TRANSITIONS
ELECTROFISSION
ELECTRON REACTIONS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FISSION
FISSION FRAGMENTS
FORM FACTORS
FUNCTIONS
HEAVY NUCLEI
INELASTIC SCATTERING
INFORMATION
ISOTOPES
LEPTON REACTIONS
MEV RANGE
MEV RANGE 10-100
MULTIPOLE TRANSITIONS
NUCLEAR FRAGMENTS
NUCLEAR REACTIONS
NUCLEI
NUMERICAL DATA
PARTICLE PROPERTIES
RADIOISOTOPES
SCATTERING
STRENGTH FUNCTIONS
URANIUM 238
URANIUM ISOTOPES
YEARS LIVING RADIOISOTOPES