Isotopic dependence of electron screening in fusion reactions

The fusion reactions 6Li(p, α)3He, 6Li(d, α)4He, and 7Li(p, α)4He have been studied over the c.m. energy range E=10 to 1450 keV. Each reaction involved the use of hydrogen projectiles and LiF solid targets as well as Li projectiles and hydrogen molecular gas targets. In all cases the effects of electron screening on the low-energy fusion cross sections (exponential enhancement) have been observed; the effects are somewhat stronger in the case of atomic p or d projectiles compared to the case of molecular H2 or D2 gas targets. If isotopic effects on electron screening are negligible, all three reactions should exhibit the same enhancements for each set of experimental techniques. The measurements confirmed this expectation to a large extent. (orig.)