Consistent microscopic study of the low-energyLi5spectrum

Nucleosynthesis in the Big Bang and in Stars

“…2.3 shows the measured low-energy S -factor (19) which clearly exceeds the S -factor expected for the reaction of the two bare nuclei. (20) The latter S-factor curve, however, agrees nicely with the data at slightly higher energies ( E 40 keV), where electron screening effects should become negligible. As in the plasma case, the nuclear separation during the penetration process (R 0.02 Å at E = 6 keV) is far inside the electron cloud of the atomic 3 He target, and the calculated screening effect of the electrons in the nuclear collision is to effectively provide a constant energy increase E. (18) As E << E, one finds (2.36)…”

“…Note that at these required high temperatures, the protons and α-particles produced react far too rapidly with the nuclides present, like 12 C, 16 O, 20 Ne, and 24 Mg, to build up large enough equilibrium abundances for further hydrostatic hydrogen or helium burning. An important reaction chain that can occur within carbon burning is…”

“…Hydrostatic Ne-burning begins at temperatures near 10 9 K and continues up to about 1.5 x 10 9 K. This process actually consists of the reactions, 20 Ne + → 16O + 20 Ne + → 24 Mg +…”

“…Helium burning in red giants essentially stops with the production of 16 O, as the subsequent 16 O(α, γ) 20 Ne reaction is very slow at helium burning temperatures (101) (there is no normal-parity "resonance" near the α-threshold (117) of 20 Ne). Thus, during helium burning, helium is built mainly into 12 C and 16 O, where the relative amounts of the two nuclides depend very sensitively on the relative triple-alpha and 12 C(α, γ) 16 O fusion cross sections.…”

“…(23) Laboratory electron screening effects have also been established for other light nucleus reactions. Remarkably, the screening energies, E, that have been extracted from the data by employing relation (2.36) 4 He data (19) with the theoretical S-factor for bare nuclei (dashed curve (20) ), bare nuclei corrected for electron screening effects in the exact adiabatic limit (solid curve), and for a correction based on the universal screening potential of Ref. 21 (dashed-dotted curve).…”