Is germanium (Ge, Z = 32) a neutron-capture element?

Abstract

Historically,Ge has been considered to be a neutron-capture element. In this case, the r-process abundance of Ge is derived by subtracting the s-process abundance from the total abundance in the Solar system. However, the Ge abundance of the metal-poor star HD 108317 is lower than that of the scaled residual r-process abundance in the Solar system, about 1.2 dex. In this paper, based on a comparison of the Ge abundances of metal-poor stars and stellar yields, we find that the Ge abundances are not the result of the primary-like yields in massive stars and come mainly from the r-process. Based on the observed abundances of metal-poor stars, we derived the Ge abundances of the weak r-process and main r-process. The contributed percentage of the neutron-capture process to Ge in the Solar system is about 59 per cent, which means that the contributed percentage of the Ge residual abundance in the Solar system is about 41 per cent. We find that the Ge residual abundance is produced as secondary-like yields in massive stars. This implies that the element Ge in the Solar system is not produced solely by the neutron-capture process.