Spin inhibition in γ-decay probabilities for states above Sn in Sm and Dy nuclei

When a compound nucleus is formed at an excitation energy above the neutron-separation threshold, it is assumed that its de-excitation will proceed via neutron emission. However, if the excited nucleus is in a high-spin state, but does not have enough excitation energy to conserve angular momentum by either photon emission after neutron emission or relative angular momentum carried off by the neutron, the nucleus will de-excite via gamma-emission instead. This effect, the spin inhibition, provides an insight into the structure of the compound nuclei and can aid the understanding of the distribution of the populated spin states in a compound nuclear reaction. In this work, the effects of spin inhibition on the gamma-decay probabilities from states in Sm-146,Sm-147 and Dy-160 are presented. For high-spin states above the S-n, spin inhibition is able to suppress neutron emission, and de-excitation via gamma-ray emission is observed for states up to 3 MeV above the S-n.

Automated summary

When a highly excited nucleus in a high-spin state cannot conserve angular momentum through neutron emission, it undergoes de-excitation via gamma-ray emission instead. The spin inhibition phenomenon provides insights into the compound nucleus structure and the distribution of spin states in compound nuclear reactions.