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, 65}Cu and ^{58, 60, 62}Ni 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.