Differential chemical abundances of heavy elements in solar twins

In this work we present differential chemical abundances of neutron-capture elements (Z>30) in solar twins. We have obtained high resolution (R = 60,000) and high S/N (> 100) spectra of solar twins in the ultraviolet region (310-400nm) with the UVES spectrograph at the VLT/ESO. In the same configuration we also observed that the Sun, that is our reference for the differential analysis, thus obtaining results with high accuracy and precision. In the ultraviolet there is a large number of atomic transitions of heavy elements, which allows the detailed study of the r and s processes. Our sample of solar twins covers a wide range of ages, so it will be possible to study the temporal evolution of the neutron capture elements.