Electron screening in 7Li and 6LiHe for different environments

The electron screening in the Li-7(p, alpha)alpha reaction has been studied at E-p = 30 to 100 keV for different environments: Li2WO4 insulator, Li metal, and PdLi alloys. For the insulator a screening potential energy of U-e = 185 +/- 150 eV was observed, consistent with previous work and the atomic adiabatic limit. However, for the Li metal and the PdLi alloys we find large values of U-e = 1280 +/- 60 and 3790 +/- 330 eV, respectively: the values can be explained by the plasma model of Debye applied to the quasi-free metallic electrons in these samples. Similar results have been found for the Li-6(p, alpha)He-3 reaction supporting the hypothesis of the isotopic independence of the electron screening effect. The data together with previous studies of d(d, p)t and Be-9(p, alpha)Li-6 in metals verify the Debye model scaling U-e proportional to Z(t) (charge number of target