Bi cluster ions are among the most utilized primary sources for time-of-flight secondary ion mass spectrometry (TOF-SIMS). Although Bi clusters have advantages over larger clusters, such as C60+ and Arn+, TOF-SIMS is less sensitive for macromolecules when Bi clusters are used as primary ions. Matrix-enhanced SIMS is a more sensitive technique for large molecules, because the matrix limits fragmentation. The matrix is thought to reduce molecular crystallinity and cohesiveness, which facilitate the extraction of large molecules from the sample surface. In this study, the authors investigate the effects of polyethylene glycol structure on the molecular sensitivity of TOF-SIMS using different primary Bi ion species. The results indicate that amorphous PEG enables the detection of larger molecules than crystalline PEG by TOF-SIMS when either Bi1+ or Bi32+ ions are used for irradiation. This suggests that the structures of organic molecules affect the propagation of kinetic energy from the primary ions. This phenomenon reduces damage to polymer chains and enhances the sensitivity of TOF-SIMS for intact molecular ions.

中文翻译：

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聚合物结晶对使用 Bi1+ 和 Bi32+ 离子的 TOF-SIMS 测量中分子灵敏度的影响

Bi 簇离子是飞行时间二次离子质谱 (TOF-SIMS) 中最常用的主要来源之一。尽管 Bi 团簇比 C60+ 和 Arn+ 等较大的团簇具有优势，但当 Bi 团簇用作主要离子时，TOF-SIMS 对大分子的敏感性较低。基质增强 SIMS 是一种对大分子更敏感的技术，因为基质限制了碎裂。基质被认为会降低分子结晶度和内聚性，这有助于从样品表面提取大分子。在这项研究中，作者使用不同的主要 Bi 离子种类研究了聚乙二醇结构对 TOF-SIMS 分子灵敏度的影响。结果表明，当使用 Bi1+ 或 Bi32+ 离子进行辐照时，无定形 PEG 能够通过 TOF-SIMS 检测到比结晶 PEG 更大的分子。这表明有机分子的结构会影响初级离子的动能传播。这种现象减少了对聚合物链的损伤，并提高了 TOF-SIMS 对完整分子离子的灵敏度。