A new excitation scheme for direct analysis of organic compounds in condensed phase is described. The approach involves the combined use of two laser-ablation based techniques (laser ionization mass spectrometry (LIMS) and laser induced breakdown spectrometry (LIBS)) within a common experimental setup to simultaneously obtain atomic and molecular information capable of discriminating organic isomers. An initial laser pulse tailored to induce gentle excitation with limited fragmentation is followed by a second pulse at a specific fluence above the plasma formation threshold. Under a simultaneous ion-photon detection scheme, this configuration allows the recording of optimized optical emission and mass spectra. Despite the consecutive excitation, the low fluence conditions of the first pulse assure the sample integrity for the LIBS analysis of the successive pulse. The improved capabilities of the new excitation scheme have been demonstrated in the analysis of three dinitrotoluene isomers (2,3-, 2,4- and 2,6-), where the information provided by LIMS and LIBS is processed by a discriminant function analysis method to establish discrimination criteria for the three nitro aromatic isomers based on differences in spectral features.

中文翻译：

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激光诱导击穿光谱法和激光电离质谱法使用量身定制的成对脉冲激发方案鉴别冷凝相中的异构体

描述了一种直接分析凝聚相中有机化合物的新激发方案。该方法涉及在共同的实验装置中结合使用两种基于激光烧蚀的技术（激光电离质谱（LIMS）和激光诱导击穿光谱（LIBS）），以同时获得能够区分有机异构体的原子和分子信息。经过定制的初始激光脉冲经过调整后可以诱导产生有限碎片的轻度激发，其后是第二脉冲，其特定通量在等离子体形成阈值以上。在同时进行的离子-光子检测方案下，此配置允许记录优化的光发射和质谱图。尽管有连续的激励，第一个脉冲的低能量密度条件确保了连续脉冲的LIBS分析的样品完整性。在分析三种二硝基甲苯异构体（2,3-，2,4-和2,6-）时，已证明了新激发方案的改进功能，其中通过判别函数分析处理了LIMS和LIBS提供的信息方法根据光谱特征的差异建立三种硝基芳族异构体的判别标准。