Willingham D, Kucher A, Winograd N
Chemistry Department, Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA.
Chem Phys Lett. 2009 Jan 22;468(4-6):264-269. doi: 10.1016/j.cplett.2008.11.094.
Photoionization of molecules sputtered from molecular thin films has been achieved using high field 125 fs pulses in the mid-IR spectral range. Using several model systems, we show that it is possible to significantly reduce molecular fragmentation induced by the laser field by increasing the photoionization wavelength. By examining the photoionization spectra as a function of wavelength, it is apparent that the photoionization mechanism is changing from a non-adiabatic multi-electron excitation process to a process that involves tunnel ionization. The results of these observations are discussed in terms of their significance for bioimaging with focused ion beams and mass-spectrometry.
利用中红外光谱范围内的高场125飞秒脉冲，实现了对从分子薄膜溅射出来的分子的光电离。通过几个模型系统，我们表明，通过增加光电离波长，可以显著减少激光场引起的分子碎片化。通过研究作为波长函数的光电离光谱，很明显光电离机制正在从非绝热多电子激发过程转变为涉及隧道电离的过程。将根据这些观察结果对聚焦离子束生物成像和质谱分析的意义进行讨论。
