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激光质谱法探测不同状态下机动车尾气中芳香烃物质相对含量的变化 总被引:3,自引:3,他引:0
利用高灵敏度、高选择性、多组分和快速实时分析探测的方法——激光质方法研究机动车尾气。发现在266nm激光作用下,低速状态下机动车尾气中的芳香族含量远高于加速状态下的含量。 相似文献
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The multiphoton ionization spectra of dimethylamine are given in the 445-470 nm region. A time of flight mass spectrometer was used,and experiment was done under collision free condition. It is found that (2+2) resonance enhanced multiphoton ionization through (nN,3s) Rydberg state produces parent ions which endure pseudo-α and C—N bond cleavages. The former forms CH3N+H=CH2 ions,and the latter gives CH2=N+H2 ions . 相似文献
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硫化氢分子的共振增强多光子电离谱 总被引:1,自引:1,他引:0
利用激光质谱法在 4 2 3~ 4 62nm范围内获得了环境污染气体硫化氢分子的共振增强多光子电离 (REMPI)谱 ,在其REMPI谱中共观察到 8个谱峰 ,其中有两个谱峰是新发现的 ,并对它们进行了试探性标识。另外还从多个角度对硫化氢分子的多光子电离解离 (MPID)机理进行了分析 ,推论出其MPID过程应属于母体离子碎裂模式。 相似文献
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有机污染正越来越引起人们的注意,然而现有的对包括具有致癌作用的最大的一类化学物质芳香烃在内的许多有机物的分析方法需要对含有污染物的气体进行预先处理.其主要缺点是复杂耗时,不能做到理想的实时在线分析.激光质谱法通过共振增强多光子电离(REMPI)把紫外光谱和飞行时间质谱(TOF-MS)结合起来,具有高灵敏度、高选择性和分析速度快的特点.在介绍了激光质谱法的原理后,介绍了一小型化的可移动激光质谱装置,其中使用一台小型KrF准分子激光器(248 nm),可以对芳香烃进行多组分检测.该装置对机动车尾气的实时测量结果表明激光质谱法用于污染分析时具有其他分析手段很少能同时具备的一些显著优点:多组分探测,在机动车尾气中同时测量到苯、甲苯、二甲苯、三甲苯、萘和甲基萘等多种芳香烃污染物;灵敏度高(0.1mg/m3);测量速度快(0.1 s);对样品不经处理,进行直接分析. 相似文献
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Multiphoton Ionization (MP) Mass Spectra of n-C3H7I AND i-C3H7I are obtained using a time-offlight mass spectrometer at 532 nm. No parentions are observed in MPI of both isomers. N-propyl cation dissociates more extensively than isopropyl cation. The C2H+5(M/Z=29) ion is observed instead of C2H+4(M/Z=28) ion in MPI of n-C3H7I, in contrast to i-C3H7I. It is found that parent molecules are first two-photon resonantly excited to A-band, then go through dissociation. Fragment ions are produced by ionization and dissociation of neutral fragments. We present directly the diss ociation pathways of n-propyl cation according to the results proposed by Levine using maximum entropy formalism. Moreover, those of isopropyl cation are discussed in this paper through branching ratio analyses. 相似文献
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二乙胺分子的多光子电离:"梯转换"过程 总被引:1,自引:0,他引:1
The multiphoton ionization (MPI) of diethylamine is first reported in this paper. A time-of-flight mass spectrometer was used in the experiment under collision-free condition. MPI mass spectra were measured in the region of 464 ~486 nm using a dye laser and at double frequency of a Nd:YAG laser. Molecular ion was created through resonance enhanced multiphoton ionization (REMPI) via Rydberg states. Fragment, ion distribution was formed through “ladder switching” process. The experimental demonstration of the process is reported for the first time by the discussion of dependence of ion relative, abundance on laser wavelength and energy. The competition between further up-pumping and fragmentation of Parent ion also exists, and higher laser intensity favors the former. 相似文献