溴苯分子和间二溴苯分子的多光子解离电离质谱研究

【作者】 刘建苹；

【导师】 孔祥和；

【作者基本信息】 曲阜师范大学 ， 物理电子学， 2007， 硕士

【摘要】 溴苯类化合物在生产生活中被广泛应用，因而大量存在于土壤和水中。作为环境荷尔蒙类物质，此类化合物对人体健康有害，在其上升到对流层后，被紫外光光解会产生卤素原子，触发一系列化学反应，破坏臭氧分子，导致臭氧层的消耗，研究其多光子电离-解离过程可以更好的控制化学反应，所以研究溴苯类化合物的光解对环境保护有着重要意义。本论文中，作者通过激光、分子束和飞行时间质谱对溴苯与1，3-二溴苯的多光子解离电离作了系统的研究。（1）利用多光子电离与飞行时间质谱技术，在266nm和355nm激光作用下探测得到了溴苯分子解离电离质谱图。经分析认为355nm激光作用下，没有发生明显的解离电离。在266nm激光作用下，获得了溴苯分子的MPIF-TOF质谱。实验测得了各碎片离子占总离子信号的百分比对激光强度的依赖关系，并用这些实验结果对溴苯分子的多光子电离解离机理做了分析，还对C₆H₅⁺，C₅H₃⁺，C₄H₂⁺，C₃H⁺等碎片离子的可能形成过程作了讨论，结果证明母体分子吸收光子解离是主要通道，且碎片离子主要是经过离子离解阶梯模式产生的。（2）在相同的实验条件下，研究了1，3-二溴苯分子的多光子解离电离过程。在266nm激光作用下其过程也主要是母体分子解离—中性碎片电离的过程，通过分析其分子的MPIF-TOF质谱，及观测各碎片离子占总离子信号的百分比对激光强度的依赖关系，得出产生的C₆H₄⁺，C₅H₃⁺，C₄H₂⁺，C₃H⁺等碎片离子主要是经过离子离解阶梯模式产生的，并推断出1，3-二溴苯母体分子和碎片离子可能的解离通道。更多还原

【Abstract】 The compound of bromobenzene is widely applied in the production life. Thus, it exists in the soil and water in large quantity. Being the environment hormone class material, this kind of compound is harmful to the health of human body. Once it rises to the convection layer, the material will yield halogen atom by the ultraviolet ray photolysis. This will trigger a series of chemical reaction, and the ozone molecule is destroyed. And the course will cause the consumption of the ozone layer. Multiphoton ionization-dissociation process is studied in order that chemical reaction can be controlled better. So the study of photolysis of the monobromo-benzene class compound is significant to the protection of environment.In this thesis, the Multiphoton ionization-dissociation process of bromobenzene and 1,3-dibromobenzene is researched in detail through the mass spectra of the laser, molecular beam and flight time.（1）With the technique of multiphoton ionization and flight time mass spectra, the ionization-dissociation mass spectrogram of bromobenzene molecular can be detected under the effect of laser whose wavelength is 266nm and 355nm.After analysis, we get the conclusion that there is no obvious ionization-dissociation with the effect of the laser of 355nm, while under the effect of the laser of 266nm, MPIF-TOF mass spectrogram of bromobenzene molecular can be got with the method of mass spectra of multiphoton ionization-flight time. The experiment measured the dependency relation between the laser intensity and the signal percent of fragment ions out of all ions. Then, we analyzed the mechanics of multiphoton ionization-dissociation with the experimental results. Furthermore, we discussed the possible establishment of fragment ions such as C₆H₅⁺, C₅H₃⁺, C₄H₂⁺, C₃H⁺ . The result shows that the absorption of photon dissociation is the main channel, and most of ion fragments are produced by ion-fragment dissociation staircase. （2）In the same experiment condition the multi-photon dissociation-ionization process of 1, 3-dibromobenzene were researched. Under the effect of 266nm laser its process is also mainly parent molecule dissociation and ionization of neutral fragment. We analyzed MPIF-TOF mass spectrogram of 1,3-dibromobenzene molecular and observed the dependency relation between the laser intensity and the signal percent of fragment ions out of all ions. The result shows that fragment ions such as C₆H₅⁺, C₅H₃⁺, C₄H₂⁺, C₃H₂⁺, are mainly generated by ion-fragment dissociation staircase. We also deduced the possible dissociation channel of 1,3-dibromobenzene parent molecule.更多还原