飞行时间质谱中光发射电子碰撞电离过程  

Laser Induced Photoelectron Impact Ionization in Timeofflight Mass Spectrometer*

作　　者：王利[1] 李海洋[1] 白吉玲[1] 孙巨龙[1] 吕日昌[1] 

机构地区：[1]中国科学院大连化学物理研究所分子反应动力学国家重点实验室

出　　处：《Chinese Journal of Chemical Physics》1998年第1期52-56,共5页化学物理学报（英文）

基　　金：国家自然科学基金

摘　　要：在飞行时间质谱仪上用３０８ｎｍ激光研究ＮＯ／Ａｒ激光多光子电离过程中，发现产生了Ａｒ及ＮＯ的高价离子现象。飞行时间质谱峰宽表明，这种电离过程是在很短的时间内进行的（＜５０ｎｓ）；从离子的质谱峰形分析得到离子产生的空间分布是连续分布在排斥极－拉出极之间的；延时脉冲加速场实验结果表明，当电场落后于激光０．２μｓ时，离子信号消失，综合实验结果，我们提出了拉出极栅网表面光发射电子碰撞电离机理。Multiple charged ions of Ar and NO were observed in MP1 experiment by 308nm excimer laser in time of flight mass spectrometer(TOFMS)FWHM of ion peak in time of flight mass spectra indicated that the ionization process was in a very short time scale(<50ns)Detailed analysis about the nascent spatial distribution of Ar ions indicated that the ions were continuously distributed between the repeller plate and the extractor gridA delayable pulsed accelerating filed was used to investigate the ionization processThe result of delay experiment showed clearly that no ion was produced when arrival of the pulsed accelerating filed was only 02μs after arrival of the laser beam. Photoemission electrons, ejected from the extractor grid surface under irradiation of a laser beam,were suggested to play an important role in the ionization process. Electrons were accelerated by the electric filed between the repeller plate and the extractor grid and ionized the gas species in the way. MPI or LDI process were completely ruled out.

关 键 词：飞行时间质谱 高价离子 氩 一氧化氮 碰撞电离 

分 类 号：O657.6[理学—分析化学]