Nonstatistical effects observed with 52Cr + n resonances
The neutron total and neutron capture cross sections of 52Cr 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. Subsequent values for the average resonance parameters for 2-wave and p-wave neutron resonances are D(0)=(43.4 +- 4.7) keV and S(0)=(2.85 +- 0.25) x 1.0 E-4 up to 1 MeV, and D(1)=14.7 keV and S(1)=(0.30 +- 0.05) x 1.0 E-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 behaviour of the p-wave level density shows that the level density parameter 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 behaviour may be explained by doorway structures with a small energy spread of states, as has been observed for 28Si and 32S which, like 52Cr, have a multiple of four nucleons in the target nucleus.
Bibliographic Reference: Article: Physical Review C, Volume 39 (1989), No. 2, pp. 426-439
Record Number: 199010078 / Last updated on: 1994-12-01
Original language: en
Available languages: en