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

Abstract

In order to investigate the screening effect of a nuclear reaction in a liquid metal environment, thick-target yields of the 6 Li(d,α) 4 He and 7 Li(p,α) 4 He 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 Δ U = 235 ±63 ( 6 Li+d) and 140±82 eV ( 7 Li+p), although the screening energy for liquid Li has a large uncertainty with U liq ∼486–776 ( 6 Li+d) and 324–637 eV ( 7 Li+p) owing to the uncertainty of the astrophysical bare S ( 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.