Lasers with pulse lengths from nanoseconds to femtoseconds and wavelengths from the mid-infrared to extreme ultraviolet (UV) have been used for desorption or ablation in mass spectrometry. Such laser sampling can often benefit from the addition of a second laser for postionization of neutrals. The advantages offered by laser postionization include the ability to forego matrix application, high lateral resolution, decoupling of ionization from desorption, improved analysis of electrically insulating samples, and potential for high sensitivity and depth profiling while minimizing differential detection. A description of postionization by vacuum UV radiation is followed by a consideration of multiphoton, short pulse, and other postionization strategies. The impacts of laser pulse length and wavelength are considered for laser desorption or laser ablation at low pressures. Atomic and molecular analysis via direct laser desorption/ionization using near-infrared ultrashort pulses is described. Finally, the postionization of clusters, the role of gaseous collisions, sampling at ambient pressure, atmospheric pressure photoionization, and the addition of UV postionization to MALDI are considered.

中文翻译：

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激光解吸与激光去离子化相结合进行质谱分析。

脉冲长度从纳秒到飞秒，波长从中红外到极紫外（UV）的激光已用于质谱仪中的解吸或烧蚀。此类激光采样通常可受益于添加第二个激光来中和中性离子。激光后电离提供的优势包括：放弃基质应用的能力，高横向分辨率，电离与解吸的解耦，改进的电绝缘样品分析，以及在最大程度减少差异检测的同时实现高灵敏度和深度分析的潜力。在通过真空紫外线辐射进行阳离子化的描述之后，考虑了多光子，短脉冲和其他阳离子化策略。在低压下进行激光解吸或激光烧蚀时，应考虑激光脉冲长度和波长的影响。描述了通过使用近红外超短脉冲的直接激光解吸/电离进行的原子和分子分析。最后，考虑了团簇的去离子化，气体碰撞的作用，在环境压力下的采样，大气压下的光去离子化以及在MALDI中添加了紫外线去离子化。