Transmission Electron Diffraction at 200 eV and Damage Thresholds below the Carbon K Edge.
Transmission Electron Diffraction at 200 eV and Damage Thresholds below the Carbon K Edge.
复制标题
200 eV 处的透射电子衍射和碳 K 边缘以下的损伤阈值。
DOI：
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发表时间：
2000
影响因子：
2.8
通讯作者：
Spence
中科院分区：
文献类型：
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作者：
Stevens;Chen;Weierstall;Spence
在定制的低能电子传输 (LEET) 室中记录了束能量为 200 eV-1 keV 的超薄芳香族和脂肪族有机薄膜的透射电子衍射图案。当束流能量从 400 eV 降低到 200 eV 时，芳香族苝薄膜的分子损伤截面显着减小（通过衍射斑点的褪色测量）。脂肪族十四烷的相应测量显示出较小的“阈值能量”，并讨论了差异。其他芳香族材料的电子束损伤也在低能量下进行了研究。碳 K 壳层电离截面和测量的损伤截面的比较表明，碳 K 壳层电离与束流能量高于 284 eV 时在芳烃中观察到的损伤密切相关。计算单个分子成像所需的最小晶胞数量，以及计算弹性与测量的损伤横截面的比较，都表明用低能电子对生物分子成像的新可能性。
Transmission electron diffraction patterns from ultra-thin aromatic and aliphatic organic films at beam energies of 200 eV-1 keV have been recorded in a custom low energy electron transmission (LEET) chamber. A significant reduction of the molecular damage cross-section, measured by fading of diffraction spots, was found for thin films of the aromatic perylene when the beam energy was reduced from 400 to 200 eV. The corresponding measurements for the aliphatic tetracontane showed a smaller "threshold energy" and the differences are discussed. Electron beam damage from other aromatic materials has also been studied at low energy. Comparison of the carbon K shell ionization cross-section and the measured damage cross-sections show that carbon K-shell ionization is strongly correlated with the damage observed in aromatics at beam energies higher than 284 eV. Calculation of the minimum number of unit cells needed for imaging a single molecule, and comparison of calculated elastic with measured damage cross-sections both indicate new possibilities for imaging biomolecules with low energy electrons.