Electron screening in nickel

Abstract

In order to investigate the interplay between nuclei and their surroundings, we studied proton-induced nuclear reactions over an energy range from 0.86 to 3.08MeV for different environments: Ni metal and NiO insulator. The measurements were based on the observation of the yields of 59, 61, 63, 64, 65Cu and 58, 60, 62Ni de-excitation $ \gamma$ -rays. Shifts in the resonance energy for the metallic target relative to the insulator one were not observed. Electron screening potential of $ U_{e}=31\pm 13$ keV was deduced for 64Ni $ (p,n\gamma )$ 64Cu reaction, while $ U_{e}=19\pm 4$ keV was deduced for 58Ni $(p,\gamma )$ 59Cu and 60Ni $(p,\gamma )$ 61Cu reactions. The observed electron screening potentials for (p,n) and (p, $\gamma$ ) reactions are the same within error bars, but the comparison with previous measurements raises the question of the independence of the electron screening from the reaction exit channel.