Calculations of the Production Cross Sections of High-Spin Isomeric States in Hafnium

The ¹⁷⁸Hf(16⁺) isomeric state has a 31-yr half-life and could pose serious radioactive activation problems in nuclear fusion reactors if its production in 14-MeV neutron-induced reactions is significant. The relatively high excitation energy (2.447 MeV) of this state causes it to lie in the continuum region. If rotational band members above this state were populated in a reaction, they would gamma cascade into it. While the existence of such levels can be justified theoretically, they have not been experimentally resolved; therefore, it is necessary to reconstruct the rotational levels built on the isomeric state. Using preequilibrium and compound nucleus theories, the cross sections for this and other hafnium isomeric states are calculated and compared with experimental measurements where available.