Electron screening in 7Li(p,α)α and 6Li(p,α)3He for different environments

The electron screening in the 7Li(p,α)α reaction has been studied at Ep=30 to 100 keV for different environments: Li2WO4 insulator, Li metal, and PdLi alloys. For the insulator a screening potential energy of Ue=185±150eV 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 Ue=1280±60 and 3790±330eV, 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 6Li(p,α)3He 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 9Be(p,α)6Li in metals verify the Debye model scaling Ue∝Zt (charge number of target).