Study of the systematics for (n,2n) reactions

The cross sections for the production of isomeric and ground states via the (n,2n) reactions on the elements arsenic, selenium, rubidium, zirconium, palladium, barium, cerium, neodymium, samarium, erbium, hafnium, and platinum; via the (n,p) reactions on iron, tin, and rhenium; and by the (n,n'γ) reactions on bromine at 14.8 MeV were measured. Isomeric activities with half-lives in the seconds range were studied with the cyclic activation technique. Long-lived isomeric and ground-state activities were investigated through Ge(Li) detector gamma-ray spectroscopy. The systematics for the (n,2n) reactions was studied. The purpose was to observe the dependence of the total cross section values on the relative neutron excess, (N-Z)/A, and the systematic trends in these values. The evidence did not confirm the existence of shell effects. The spin cut-off parameter and the number of gamma rays emitted was determined for the (n,2n) reactions on 78Se, 91Zr, 138Ba, 168Er, and 180Hf