Determining the Mn valence variation at the nanometer scale will be an important advance in the study of heterogeneous natural silicates. Here, the potential of the scanning transmission X-ray microscopy at the Mn L_2,3-edges (640–655 eV) as a probe for manganese redox state is evaluated. For this purpose, several natural Mn-silicates (rhodonite, ardennite, piemontite, Mn⁴⁺-silicate, jacobsite) were analysed to identify the spectral parameters most sensitive to the Mn valence, regardless of the coordination environment, the crystal field strength, the nature and the length of the metal–ligand bonds, and the intra-atomic Coulomb and spin–orbit interactions. Two suitable spectral empirical calibrations are thus proposed, linking the Mn valence to two peak intensity ratios: one ratio of intensities from two energy points of the L₂ peak (at 651.7 and 655.2 eV), and one ratio of intensities from one energy point of the L₂ peak (at 655.2 eV) and one of the L₃ peak (at 641.6 eV). Thank to them, the first quantitative Mn valence maps are constructed, with a high spatial resolution (<40 nm pixel size), opening the way to exhaustive crystallochemical studies of silicates containing Mn with different valences.

在纳米尺度上确定Mn价变化将是研究非均质天然硅酸盐的重要进展。在此，评估了在Mn L _2,3-边缘（640–655 eV）处作为锰氧化还原态探针的扫描透射X射线显微镜的潜力。为此，使用了几种天然锰硅酸盐（菱锰矿，石，钙蒙脱石，Mn ⁴⁺-硅酸盐，雅克矿）进行了分析，以识别对Mn价最敏感的​​光谱参数，而不考虑配位环境，晶体场强度，金属-配体键的性质和长度以及原子内库仑和自旋–轨道相互作用。因此，提出了两个合适的光谱经验校准，将Mn价与两个峰强度比联系起来：一个来自L ₂峰两个能量点的强度比（在651.7和655.2 eV处）和一个来自一个能量点的强度比。 L ₂峰值（在655.2 eV处）和L _3之一峰值（641.6 eV）。多亏了他们，第一个定量的Mn价图得以构建，具有很高的空间分辨率（<40 nm像素大小），这为穷举含Mn的硅酸盐的不同价态的晶体化学研究开辟了道路。