The true purity of Roman silver coinage was hidden by enriching the surfaces of the coins. The question investigated here is whether Roman gold coins were also surfaced enriched. Two non-destructive techniques were employed to do this: X-ray fluorescence (XRF) and a ‘newer’ technique, muonic X-ray emission spectroscopy (μXES). For the latter, the momentum of the muons is controlled, allowing for the composition of the coin to be determined at various depths. Here we show that there is no surface enrichment of the Roman gold coins analysed. Furthermore, we show that XRF and μXES return congruent results at the near surface. This all supports the integrity of surface level analyses of Roman gold coins. We then discuss the broader applicability of our muon technique to the further study of Roman gold coinage, to the cultural heritage sector and to archaeological scientists more generally.

罗马银币的真正纯度是通过丰富硬币表面来隐藏的。这里考察的问题是罗马金币是否也浮出水面。为此采用了两种非破坏性技术：X 射线荧光 (XRF) 和“较新”的技术，μ子 X 射线发射光谱 (μXES)。对于后者，μ子的动量受到控制，从而可以在不同深度确定硬币的成分。在这里，我们表明所分析的罗马金币没有表面富集。此外，我们表明 XRF 和 μXES 在近表面返回一致的结果。这都支持了罗马金币表面水平分析的完整性。然后我们讨论了我们的μ子技术在进一步研究罗马金币方面的更广泛适用性，