Liquid phase transmission electron microscopy (LPTEM) is rapidly developing as a powerful tool for probing processes in liquid environments with close to atomic resolution. Knowledge of the water thickness is needed for reliable interpretation and modelling of analytical studies in LPTEM, and is particularly essential when using thin liquid layers, required for achieving the highest spatial resolutions. The log-ratio method in electron energy-loss spectroscopy (EELS) is often applied in TEM to quantify the sample thickness, which is measured relative to the inelastic mean free path (λ_IMFP). However, λ_IMFP itself is dependent on sample material, the electron energy, and the convergence and divergence angles of the microscope electronoptics. Here, we present a detailed quantitative analysis of the λ_IMFP of water as functions of the EELS collection angle (β) at 120 keV and 300 keV in a novel nanochannel liquid cell. We observe good agreement with earlier studies conducted on ice, but find that the most widely used theoretical models significantly underestimate λ_IMFP of water. We determine an adjusted average energy-loss term E_{m, water}, and characteristic scattering angle θ_{E, water} that improve the accuracy. The results provide a comprehensive knowledge of the λ_IMFP of water (or ice) for reliable interpretation and quantification of observations in LPTEM and cryo-TEM studies.

中文翻译：

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电子在水中的非弹性平均自由程。

液相透射电子显微镜（LPTEM）迅速发展为一种强大的工具，可在接近原子分辨率的液体环境中探测过程。为了可靠地解释和建模LPTEM中的分析研究，需要了解水的厚度，当使用薄的液体层时，获得最高的空间分辨率尤为重要。在电子能量损失光谱法（EELS）的对数比的方法往往是在TEM施加以量化样品的厚度，这是相对于非弹性平均自由路径（测得λ _IMFP）。然而，λ _IMFP它本身取决于样品材料，电子能量以及显微镜电子光学的会聚角和发散角。这里，我们提出了一个详细的定量分析λ _IMFP水作为EELS收集角（功能β在120千电子伏，并在纳米通道新颖液晶单元300千电子伏）。我们观察到在冰上进行的早期研究一致，但发现最广泛使用的理论模型显著低估λ _IMFP的水。我们确定调整平均能量损失术语ë_米，水，和特征性的散射角θ _E，水即提高精度。结果提供了对λ _IMFP的水（或冰）可靠的解释，并在LPTEM观察和冷冻透射电镜研究的定量。