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A previous study of correlations between element abundance ratios, [X/Fe],and ages of solar twin stars is extended to include Sc, Mn, Cu, and Ba. HARPSspectra with S/N > 600 are used to derive very precise (+/- 0.01 dex)differential abundances, and stellar ages with internal errors less than 1 Gyrare obtained by interpolation in the logg - Teff diagram between isochronescalculated with the Aarhus Stellar Evolution Code. For stars younger than 6Gyr, [X/Fe] is tightly correlated with stellar age for all elements. For agesbetween 6 and 9 Gyr, the [X/Fe] - age correlations break down and the starssplit up into two groups having respectively high and low [X/Fe] for the odd-Zelements. It is concluded that while stars in the solar neighborhood youngerthan about 6 Gyr were formed from interstellar gas with a smooth chemicalevolution, older stars have originated from regions enriched by supernovae withdifferent neutron excesses. Furthermore, the correlations between abundanceratios and stellar age suggest that: i) Sc is made in Type II supernovae alongwith the alpha-capture elements, ii) the Type II to Ia SNe yield ratio is aboutthe same for Mn and Fe, iii) Cu is mainly made by the weak s-process in massivestars, iv) the Ba/Y yield ratio for AGB stars increases with decreasing stellarmass, v) [Y/Mg] and [Y/Al] can be used as "chemical clocks" when determiningages of solar metallicity stars.

High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age