二次离子质谱仪中二次中性粒子空间分布研究  

Research of Secondary Neutral Particles Spatial Distribution of Secondary Ion Mass Spectrometer

作　　者：王培智[1] 田地[1] 龙涛[2] 王利 包泽民[1] 邱春玲[1] 刘敦一[2] 

机构地区：[1]吉林大学仪器科学与电气工程学院,吉林长春130021 [2]中国地质科学院地质研究所,北京离子探针中心,北京100037 [3]大连民族大学,辽宁大连116600

出　　处：《质谱学报》2016年第3期222-228,共7页Journal of Chinese Mass Spectrometry Society

基　　金：国家重大科学仪器设备开发专项《同位素地质学专用TOF-SIMS科学仪器》之任务二(2011YQ05006902)资助

摘　　要：为提高二次离子质谱仪(secondary ion mass spectrometer,SIMS)的灵敏度,引入了飞秒激光电离一次离子轰击溅射产生的二次中性粒子。实验以纯银、纯铜为目标样品,利用自主研制的飞行时间质谱仪分析二次后电离的离子,研究二次中性粒子的后电离效率和空间分布。结果表明:飞秒激光电离技术可将仪器的灵敏度提高70倍以上;飞秒激光电离出的107 Ag+和109 Ag+的同位素丰度比值误差为0.8%;二次中性粒子的空间分布符合Maxwell-Boltzmann模型。该结果可为在设计方法上提高SIMS仪器灵敏度提供依据。To improve the sensitivity of the secondary ion mass spectrometer （SIMS）, the secondary neutral particles was introduced, which was generated by the femtosecond laser ionizing the primary ion bombardment with the instantaneous power of 7 × 10^18 W/cm^2. In this experiment, the primary ion of oxygen shotted the surface of the sample with 15 keV energy and 45° angle, which was made of pure silver and pure copper. About 1.2 mm above the sample surface, the femtosecond laser was introduced and the secondary neutral particles were ionized by the former. With the impact of the extraction electrode electric field, the ion was bombarded by the primary ion and the remarkably improved by the femtosecond laser post-ionization counting. The error of the isotope ratio of the ^107Ag^＋ and ^109Ag^＋ ionized by the femtoseeond laser was 0.8%, while that of the ^107Ag^2＋ and ^109Ag^2＋ was 5.8%, and that of ^107Ag^＋ and ^109Ag^＋ ionized by the primary ion bombardment was 5.7%. It was because the femtosecond laser ionized the Ag particles mainly to the monovalent ^107 Ag^＋ and ^109Ag^＋ , and the quantity of the bivalent ^107Ag^2＋ and ^109Ag^2＋ were fewer compared to the monovalent ones. The productive rate was in the same order of magnitudes compared to that generated by the primary ion bombardment, and the fewer productive rate directly impacted the measurement accuracy of the instrument. Because the productive rate of ^107Ag^＋ and ^109Ag^＋ ionized by the femtosecond laser was much greater than those two formers, the isotope ratio was more approximate to the theoretic result. Therefore it demonstrated that the adhibition of the femtosecond laser greatly improved the productive rate of the secondary ion and the instrument measurement accuracy, which helped the quantitative analysis becoming easier. When the energy of primary ion was 15 keV, to delay the time between the primary ion and the post-ionization laser, the spatial and velocity distribution of the neutral particles generated in the bombardment

关 键 词：二次离子质谱(SIMS) 飞秒激光后电离 中性粒子 

分 类 号：O657.63[理学—分析化学] TH84[理学—化学]