The calculation of neutron cross-sections from optical potentials

Nuclear model calculations on proton and deuteron induced reactions on 122Te and 120Te with particular reference to the formation of the isomeric states 120m,gI

Nuclear model calculations were performed on (p,xn) reactions on 122Te and 120Te, and (d,xn) reactions on 120Te. The computer code used (STAPRE) incorporates statistical and precompound models as well as nuclear structure effects. The total cross-sections of (p,xn) and (d,xn) processes leading to the formation of the radioisotopes 119I, 120gI, 121I and 122I are described well by the calculations. The isomeric cross-section, however, is rather difficult to calculate. The yield of the high spin isomer (120mI) depends on the type of reaction involved and increases with the increasing projectile energy. From an analysis of the energy dependence of the isomeric cross-section ratio, the excitation energy of 120mI was deduced to be 550+/-50 keV and its spin and parity as 4+. The experimental data reported earlier and the theoretical analysis presented in this work allow to define the optimum conditions for the production of the medically important beta+ emitter 120gI with enhanced confidence.