RADIATIVE TRANSITIONS FROM NEUTRON-CAPTURE IN CR-53 RESONANCES

A measurement is described of gamma-ray spectra emitted after neutron capture in s- and p-wave resonances of Cr-53, in the range 2-50 keV. The observed decay scheme concerns 38 excited levels of Cr-54, with energies up to 5.6 MeV. New information is obtained on the multiplicity of gamma cascades, on the spin and parity of Cr-54 levels, and on the spin of neutron resonances of Cr-53. Partial El and Ml radiative widths are obtained for transition energies from 4.1 to 9.7 MeV. The overall energy behaviour of E1 reduced widths is in rough agreement with a Lorentzian shape, but the average intensity is higher than expected from photo-neutron data. The measured average E1 strength is (S(El)) = (8.7 +/-+/- 0.8).10(-15) MeV-5. Fluctuations around this average are non-random, showing the existence of an intermediate structure. Reduced E1 widths are strongly correlated with the reduced neutron widths in the whole energy interval. An indication is found for a correlation between reduced El widths and spectroscopic factors of Cr-54 levels. The measured average Ml strength [k(M1)] = (5.9 +/- 0.7).10(-9) MeV-3 appears to be energy-independent as in the single-particle model.