A study of 56Fe(n,xnγ) reactions at 14.6 MeV

A study of the 56Fe(n,xnγ) reactions, x=1,2 was undertaken with the aim to get more information about deexcitation modes of highly excited levels of sup(56,57)Fe. The experiment made use of a 4-detector in-beam setup where a significant background reduction was achieved by fast timing techniques. Cross sections for a population of 14 discrete transitions were determined. The results are in favour of the dominant role of the statistical reaction mechanism which should be supplemented by direct processes. The structure of highly excited levels of 56Fe does not seem to be completely described by the nondeformed many quasiparticle wave function. Average γ-multiplicities in the (n,n'γ) channel were measured, the overall average length of cascades being 4.0 +-0.4. Deduced entry energies of cascading γ-rays support the previous observation about unexpectedly large γ-competition above the neutron binding and suggest that by γ-emission especially the high spin levels of this region suffer. (author)