A mid‐infrared free‐electron laser (MIR‐FEL) is a synchrotron‐radiation‐based femto‐ to pico‐second pulse laser. It has unique characteristics such as variable wavelengths in the infrared region and an intense pulse energy. So far, MIR‐FELs have been utilized to perform multi‐photon absorption reactions against various gas molecules and protein aggregates in physical chemistry and biomedical fields. However, the applicability of MIR‐FELs for the structural analysis of solid materials is not well recognized in the analytical field. In the current study, an MIR‐FEL is applied for the first time to analyse the internal structure of biological materials by using fossilized inks from cephalopods as the model sample. Two kinds of fossilized inks that were collected from different strata were irradiated at the dry state by tuning the oscillation wavelengths of the MIR‐FEL to the phosphoryl stretching mode of hydroxyapatite (9.6 µm) and to the carbonyl stretching mode of melanin (5.8 µm), and the subsequent structural changes in those materials were observed by using infrared microscopy and far‐infrared spectroscopy. The structural variation of these biological fossils is discussed based on the infrared‐absorption spectral changes that were enhanced by the MIR‐FEL irradiation, and the potential use of MIR‐FELs for the structural evaluation of biomaterials is suggested.

中文翻译：

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中红外自由电子激光在生物材料结构分析中的应用

中红外自由电子激光器（MIR-FEL）是一种基于同步辐射的飞秒到皮秒脉冲激光器。它具有独特的特性，例如红外区域的可变波长和强烈的脉冲能量。迄今为止，MIR-FELs已被用于物理化学和生物医学领域对各种气体分子和蛋白质聚集体进行多光子吸收反应。然而，MIR-FEL 在固体材料结构分析中的适用性在分析领域还没有得到很好的认可。在目前的研究中，首次应用 MIR-FEL 以头足类动物的化石墨水作为模型样本来分析生物材料的内部结构。通过将 MIR-FEL 的振荡波长调整为羟基磷灰石的磷酰基拉伸模式 (9.6 µm) 和黑色素的羰基拉伸模式 (5.8 µm)，从不同地层收集的两种化石墨水在干燥状态下进行辐照，然后使用红外显微镜和远红外光谱观察这些材料的随后结构变化。基于 MIR-FEL 辐射增强的红外吸收光谱变化讨论了这些生物化石的结构变化，并提出了 MIR-FEL 在生物材料结构评估中的潜在用途。并且通过使用红外显微镜和远红外光谱观察这些材料随后的结构变化。基于 MIR-FEL 辐射增强的红外吸收光谱变化讨论了这些生物化石的结构变化，并提出了 MIR-FEL 在生物材料结构评估中的潜在用途。并且通过使用红外显微镜和远红外光谱观察这些材料随后的结构变化。基于 MIR-FEL 辐射增强的红外吸收光谱变化讨论了这些生物化石的结构变化，并提出了 MIR-FEL 在生物材料结构评估中的潜在用途。