Screening Potential of 6Li(d,α)4He and 7Li(p,α)4He Reactions in Liquid Lithium

In order to investigate the screening effect of a nuclear reaction in a liquid metal environment, thick-target yields of the Li-6(d,alpha)He-4 and Li-7(p,alpha)He-4 reactions were measured using a liquid Li target for incident energies between 22.5 and 70 keV. The modified S(E) factor [S* (E)] for the liquid Li environment was deduced by dividing the measured yield by the energy integration of the penetration factor divided by the stopping power. It was shown that S* (E) for the liquid environment is considerably larger than that for the atomic/molecular environment for both reactions. The difference in the screening energy between the two environments was deduced to be Delta U = 235 +/- 63 (Li-6+d) and 140 +/- 82 eV (Li-7+p), although the screening energy for liquid Li has a large uncertainty with U-liq similar to 486-776 (Li-6+d) and 324-637 eV (Li-7+p) owing to the uncertainty of the astrophysical bare (E) factors. This difference in the screening energy should be considered in such a way that, in liquid Li metal, conduction electrons and Li+ ions contribute to the screening in addition to bound electrons.