Limitations in the Study of Cultural Heritage Objects With Atomic Spectroscopy

The study of cultural heritage objects, such as coins, using techniques from nuclear physics including x-ray fluorescence (XRF) and proton induced x-ray emission (PIXE) has been in practice for many years. These methods have been used because of their non-destructive nature, but this gentleness comes with a set of important challenges. The limitations of these methods, such as silver surface enrichment and inconsistency between analysis techniques, have been previously characterized and are well documented. A challenge that is less well documented is that of surface inconsistency. In this study, XRF, PIXE, and EDS were used on a set of 20 Ancient Roman Denarii to qualify and quantify this surface level inhomogeneity. Data were taken using varying beam sizes and at varying locations in an attempt to provide the most complete view of each sample. Data from small spots were then compared with large-scale XRF maps of each coin. It was concluded that researchers should be concerned with both the cross-sectional inhomogeneity and surface inconsistency. The addition of surface analysis will allow researchers to most fully contribute to the dialogue about how physical objects are woven into cultural history.