Solar Abundance of Elements from Neutron-capture Cross Sections

Introduction: Light elements, H and He, covering the solar surface are widely believed to be dominant inside the Sun [1]. Noting that gaseous envelopes may not reflect the Sun’s internal composition, Harkins [2] used analyses on 443 meteorites to conclude that Fe, O, Ni and Si are more abundant. B2FH [3] explained element synthesis in stars; decades later Fowler said laboratory and theoretical calculations cannot explain why O/C = 2 [4]. Solar-wind-implanted elements in lunar soils showed a mass-dependent excess of lighter isotopes [5]. This empirical fractionation also yielded Fe, O, Ni and Si as the most abundant elements in the Sun [5, 6]. Neutron-capture cross-sections and the photospheric abundance [1] of s-process nuclides [3] offer another test for mass separation in the Sun. Composition of the Sun: Below is a widelyquoted abundance pattern of elements in the Sun [1].