Reaction mechanisms and shell structure effects in 54Fe+ 6Li and 58Ni+d reactions at medium energies

Abstract

Excitation functions and average recoil ranges for products formed in deuteron induced reactions on 58Ni and in 6Li ion induced reactions on 54Fe have been measured. The incident energies considered ranged from 4 to 40 MeV for the deuterons and from 15 to 60 MeV for the 6Li ions. The recoil range values indicate the predominance of equilibrium compound nucleus processes at energies up to several MeV beyond the peaks in the excitation functions. At still higher energies a statistical model analysis of the data indicates the increasing importance of pre-equilibrium particle emission. In the analysis, the consideration of shell effects according to Rosenzweig's model leads to greatly improved estimates of the experimental isobaric yield ratios. Evidence for direct reaction processes leading to the formation of 57Ni and 56Ni in the deuteron induced reactions and to 55Co in the lithium ion induced reactions has also been observed. The validity of the independence hypothesis is verified for excitation energies at which the recoil ranges indicate the predominance of equilibrium statistical processes in both reaction systems.