Manganese oxides are important geomaterials, widespread in terrestrial and Martian environments. Characterisation of the oxidation state of Mn is a central issue in science; this task has been addressed up to the present by X‐ray spectroscopy or diffraction techniques. The former, however, requires access to synchrotron facilities, while the latter does not provide crystal‐chemical information at the local scale. In this work, we compare a large set of Raman data from well‐characterised samples, already published by the same authors of this paper or as found in the literature. We show a clear correlation between the oxidation state of Mn and the wavenumber of peculiar bands; octahedrally co‐ordinated Mn²⁺ is recognised by a band around 530 cm⁻¹, Mn³⁺ by a band around 580 cm⁻¹ and Mn⁴⁺ by a band around 630 cm⁻¹, while tetrahedrally co‐ordinated Mn²⁺ is recognisable by a band around 650 cm⁻¹. Strongly distorted Mn³⁺ octahedra are indicated by the appearance of Jahn–Teller modes. Our method allows a reliable, easily accessible tool to characterise the oxidation states of Mn in oxides, also suitable for microscale mapping. It provides a robust analytical basis for the use of these minerals as redox indicators in geology/geochemistry, in exoplanetary research or for monitoring technological processes.

中文翻译：

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用拉曼光谱法测定锰氧化物中微量锰的氧化态的可靠方法

锰氧化物是重要的地球材料，广泛存在于陆地和火星环境中。Mn的氧化态的表征是科学中的中心问题。迄今为止，该任务已通过X射线光谱或衍射技术解决。但是，前者需要使用同步加速器设施，而后者则不提供本地规模的晶体化学信息。在这项工作中，我们比较了特征明确的样本中的大量拉曼数据，这些样本已经由本文的相同作者发表或已在文献中发现。Mn的氧化态与奇特谱带的波数之间存在明显的相关性。八面体配位的Mn ²⁺由大约530 cm ^-1的谱带识别，Mn ³⁺大约580 cm ^-1的谱带和Mn ⁴⁺大约630 cm ^-1的谱带，而通过650 cm ^-1左右的谱带可以识别四面配位的Mn ²⁺。Jahn-Teller模式的出现表明Mn ³⁺八面体严重变形。我们的方法提供了一种可靠，易于使用的工具来表征氧化物中Mn的氧化态，这也适用于微尺度绘图。它为在地质/地球化学，系外行星研究或监测工艺过程中将这些矿物用作氧化还原指示剂提供了可靠的分析基础。