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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theory and Application of Dissociative Electron Capture in Molecular Identification
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Theory and Application of Dissociative Electron Capture in Molecular Identification

机译：解离电子俘获在分子鉴定中的理论与应用

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The coupling of an electron monochromator (EM)to a mass spectrometer (MS)has created a new analytical technique,EM-MS,for the investigation of electrophilic compounds.This method provides a powerful tool for molecular identification of compounds contained in complex matrices,such as environmental samples.In particular,EM-MS has been applied to the detection of nitrated aromatic compounds,many of which are potent mutagens and/or carcinogens and are considered environmental hazards.EM-MS expands the application and selectivity of traditional MS through the inclusion of a new dimension in the space of molecular characteristics-the electron resonance energy spectrum.EM-MS also enhances detection sensitivity as well because the entire electron flux of the proper energy can be delivered into the negative ion resonance that is analytically most useful to solving the problem at hand.However,before this tool can realize its full potential,it will be necessary to create a library of resonance energy scans from.standards of the molecules for which EM-MS offers a practical means of detection.Unfortunately,the number of such standards is very large and not all of the compounds are commercially available,making this library difficult to construct.Here,an approach supplementing direct measurement with chemical inference and quantum scattering theory is presented to demonstrate the feasibility of directly calculating resonance energy spectra.This approach makes use of the symmetry of the transition-matrix element of the captured electron to discriminate between the spectra of isomers.As a way of validating this approach,the resonance values for 25 nitrated aromatic compounds were measured along with their relative abundance.Subsequently,the spectra for the isomers of nitrotoluene were shown to be consistent with the symmetry-based model.The initial success of this treatment suggests that it might be possible to predict negative ion resonances and thus create a library of EM-MS standards.
机译：电子单色仪（EM）与质谱仪（MS）的耦合创造了一种用于研究亲电化合物的新分析技术EM-MS。该方法为分子鉴定复杂基质中所含化合物提供了强大的工具， EM-MS特别用于检测硝化的芳族化合物，其中许多是强诱变剂和/或致癌物，被认为对环境有害.EM-MS通过以下方法扩展了传统MS的应用范围和选择性EM-MS还提高了检测灵敏度，因为适当能量的整个电子通量都可以传递到负离子共振中，这在分析上是最有用的，它还提高了检测灵敏度。解决这个问题的方法。但是，在此工具能够充分发挥其潜力之前，有必要创建一个共振库EM-MS提供了一种实用的检测手段来对这些分子的标准进行能量扫描。不幸的是，此类标准的数量非常大，而且并非所有化合物都可以从市场上买到，这使得该文库难以构建。提出了用化学推论和量子散射理论补充直接测量的方法，以证明直接计算共振能谱的可行性。该方法利用捕获电子的跃迁矩阵元素的对称性来区分异构体的光谱。一种验证该方法的方法，测量了25种硝化芳族化合物的共振值及其相对丰度。随后，硝基甲苯异构体的光谱显示出与基于对称性的模型一致。此方法的初步成功表明可能有可能预测负离子共振，从而建立EM-MS stan库渣ard

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