Physics Research Building, Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
Theodore Jorgensen Hall, Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
Phys Chem Chem Phys. 2019 Mar 28;21(12):6553-6558. doi: 10.1039/c8cp07866a. Epub 2019 Mar 8.
We report on the photoionization and photofragmentation of aniline (CHNH) and nitrobenzene (CHNO) under single-molecule conditions in the focus of 50 fs, 800 nm laser pulses. Ion mass spectra are recorded as a function of intensity ranging from 6 × 10 to 3 × 10 W cm. Ion yields are measured in the absence of the focal volume effect and without the need for additional deconvolution of data. We observe evidence of resonance-enhanced multiphoton ionization in aniline, in agreement with current literature. Phenyl-based ion fragments, singly-charged parent ions, and dissociative rearrangement processes are observed for both molecules. However, fragmentation in aniline is heavily suppressed in favor of parent ionization while the reverse is true for nitrobenzene, and multiply-charged parent ions are present in aniline and absent in nitrobenzene. We discuss the implications of these and other results as they relate to molecular stability against intense-field ionization and fragmentation, specifically with regards to the opposing behavior of the substituted amino and nitro functional groups.
我们在 50fs、800nm 激光脉冲的焦点下报告了苯胺（CHNH）和硝基苯（CHNO）在单分子条件下的光致电离和光碎裂。作为光强的函数，我们记录了离子质谱，范围从 6×10 到 3×10Wcm。在没有焦点体积效应的情况下测量离子产率，并且不需要对数据进行额外的反卷积。我们观察到苯胺中存在共振增强多光子电离的证据，这与当前文献一致。对于两种分子，我们都观察到了基于苯基的离子碎片、单电荷母体离子和离解重排过程。然而，在苯胺中，碎裂被强烈抑制以有利于母体离子化，而在硝基苯中则相反，并且在苯胺中存在多电荷母体离子，而在硝基苯中则不存在。我们讨论了这些和其他结果的意义，因为它们与分子对强场电离和碎裂的稳定性有关，特别是与取代的氨基和硝基官能团的相反行为有关。
