GEPI

Heavy elements, i.e. those that form beyond the iron peak, primarily form through a series of neutron-captures. Neutron-capture nucleosynthesis can be split into two distinct processes ; the slow (s-) and the rapid (r-) process. The sites where these two processes occur are very different and the timescales at which they begin to enrich the interstellar medium, and hence affect the heavy element abundances in the subsequent generation of stars, differs. Using several spectroscopic analyses, we can examine the ratios of the r- and s-process in metal-poor stars, which gives us clues to nucleosynthesis in very early stellar generations that are no longer observable. In this presentation I discuss one such technique in detail. By exploiting the hyperfine-structure (HFS) of the barium 4554 Å resonance line, one can measure the ratio of the r- and s-process in detail. As telescopes become larger and instrumentation improves, new spectroscopic features, such as convective effects in stellar atmospheres, become prominent. As a result, our methods for analysis must become more sophisticated to better model these features. I will demonstrate that such improvements to modelling techniques vastly improves upon the r- and s-process ratio obtained using less sophisticated modelling techniques.