Abstract A Thallium (Tl) L 3 -edge x-ray absorption experiment was performed on a NaI(Tl) scintillation crystal at room temperature using fluorescence detection. The data analysis provides clear evidence for a ≃ 5 % average bond length expansion of the first shell I atoms surrounding the Tl impurities with respect to the Na-I crystallographic bond-length. Possible evidence for a slight expansion of the second and third shells is obtained. The data are compatible with a previous experiment performed at liquid nitrogen temperature considering thermal expansion. A critical review of existing theoretical predictions and density functional theory supercell calculations support present findings and suggest the opportunity to perform a high quality temperature dependent experiment.

中文翻译：

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NaI(Tl) 闪烁体晶体中 Tl 置换杂质周围的局部晶格弛豫

摘要 在室温下使用荧光检测对NaI(Tl) 闪烁晶体进行铊(Tl) L 3 边X 射线吸收实验。数据分析为围绕 Tl 杂质的第一壳 I 原子相对于 Na-I 晶体键长的平均键长扩展 ≃ 5% 提供了明确的证据。获得了第二和第三壳轻微膨胀的可能证据。考虑到热膨胀，这些数据与之前在液氮温度下进行的实验相一致。对现有理论预测和密度泛函理论超胞计算的批判性审查支持了目前的发现，并提出了进行高质量温度相关实验的机会。