We have designed and constructed a combined experimental setup for synchronous measurements of electron diffraction patterns and mass-spectra of gas samples. Test measurements have been performed for acetic acid at two temperatures, 296 K and 457 K. Electron diffraction data have been analyzed taking into account mass spectra measured in the same experiments. From the diffraction intensities, molecular structures and mole fractions of the acetic acid monomer and dimer have been refined. The obtained results demonstrate the importance of measuring mass spectra in gas electron diffraction experiments. In particular, it is possible to detect the sample decomposition, which can be used for the optimization of experimental conditions and for the data interpretation. The length of the hydrogen bond in the acetic acid dimer determined in this work, re(O⋯H) = 1.657(9) Å, is in good agreement with modern theoretical predictions. We recommend measuring the diffraction patterns of acetic acid for the calibration of the sample pressure in the diffraction volume.

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比勒费尔德大学的组合气体电子衍射和质谱实验装置

我们设计并构建了一个组合实验装置，用于同步测量气体样品的电子衍射图和质谱。已在两个温度（296 K 和 457 K）下对乙酸进行了测试测量。已考虑在相同实验中测量的质谱分析了电子衍射数据。从衍射强度、乙酸单体和二聚体的分子结构和摩尔分数已经被精制。所得结果证明了在气体电子衍射实验中测量质谱的重要性。特别是可以检测样品分解，可用于优化实验条件和数据解释。在这项工作中确定的乙酸二聚体中氢键的长度，re(O⋯H) = 1.657(9) Å，与现代理论预测非常吻合。我们建议测量乙酸的衍射图以校准衍射体积中的样品压力。