Nonstatistical effects observed with /sup 52/Cr+n resonances

Journal Article · Tue Jan 31 23:00:00 EST 1989 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.39.426· OSTI ID:6529993

Rohr, G; Shelley, R; Brusegan, A; Poortmans, F; Mewissen, L

The neutron total and neutron capture cross sections of /sup 52/Cr have been measured using the neutron time-of-flight technique at a pulsed electron linear accelerator. Data analyses have been performed in the energy ranges 1 to 500 keV and 1 keV to 1 MeV, respectively, for capture and transmission, with R-matrix multilevel multichannel codes and with resonance shape fitting procedures, to determine the resonance parameters E/sub 0/, gGAMMA/sub n/, gGAMMA/sub Y/, J, and l. Subsequent values for the average resonance parameters for s-wave and p-wave neutron resonances are D/sub 0/ = (43.4 +- 4.7) keV and S/sub 0/ = (2.85 +- 0.25) x 10/sup -4/ up to 1 MeV, and D/sub 1/ = 14.7 keV and S/sub 1/ = (0.30 +- 0.05) x 10/sup -4/ up to 200 keV. The following nonstatistical effects are indicated in the resonance parameter set: two gaps are observed in the s-wave level distribution, where at least two resonances for each gap are missing; a strong discontinuity in the level spacing is observed for p-wave resonances whereby three energy ranges, up to 500 keV, with different level spacings may be distinguished. This energy-dependent behavior of the p-wave level density shows that the level density parameter (a) strongly depends on the excitation energy and causes parity dependence of nuclear states in the neutron energy range (200--500) keV. These deviations of the resonance parameters from statistical behavior may be explained by doorway structures with a small energy spread of states, as has been observed for /sup 28/Si and /sup 32/S which, like /sup 52/Cr, have a multiple of four nucleons in the target nucleus.

• Research Organization: Commission of the European Communities, Joint Research Centre, Central Bureau for Nuclear Measurements, Geel, Belgium
• OSTI ID: 6529993
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 39:2; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

651520* -- Nuclear Properties & Reactions
A=39-58
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACCELERATORS
BARYON REACTIONS
CAPTURE
CHROMIUM 52 TARGET
CROSS SECTIONS
DATA
ENERGY RANGE
EXPERIMENTAL DATA
FUNCTIONS
HADRON REACTIONS
INFORMATION
KEV RANGE
LINEAR ACCELERATORS
MATHEMATICAL MODELS
MATRICES
NEUTRON REACTIONS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUMERICAL DATA
P WAVES
PARTIAL WAVES
PARTICLE MODELS
PHOSPHORS
PLASTIC SCINTILLATORS
R MATRIX
RESONANCE
S WAVES
SHELL MODELS
SINGLE-PARTICLE MODEL
STRENGTH FUNCTIONS
TARGETS
TIME-OF-FLIGHT METHOD
TOTAL CROSS SECTIONS