飞行时间质谱仪中的离子峰漂移机理研究

摘要

文章报道了三乙胺分子在激光波长为266nm的YAG脉冲激光器下的共振多光子电离飞行时间质谱,研究发现随着激光功率密度的增加,各质量数的碎片离子的飞行时间有减小的趋势,即质谱峰发生漂移.离子的质荷比越小,信号强度越大,质谱峰漂移越明显.分析认为,飞行时间质谱峰的漂移是瞬间加减速效应和网栅吸附双重作用的结果.对于产生的碎片离子数目较少的激光电离中,网栅吸附引起的漂移占优势,但当激光电离产生的碎片离子数目较多时,瞬间加减速效应将显现.在飞行过程中受电压起伏变化影响的数值模拟与实验中获得的离子峰漂移状况相一致.%The mass spectra of triethylamine are obtained in time-of-flight mass spectrometer with the resonance enhanced multi-photon ionization technique by 266nm YAG laser.A new phenomenon is observed that the time of fight of various fragment ions decrease when the laser power density increase and keep the other conditions unchanged.The mass to charge ratio is smaller and/or ion signal intensity is bigger,the mass peak shift is more obvious.Analysis suggests that reasons for the mass peaks' shift may be the result of the superposition of the instantaneous acceleration and deceleration effects and grating ionic adsorption.The peak shift induced by the adsorption of the grating electrode has the preponderance over the instantaneous acceleration and deceleration effect when the number of fragment ions is a few in the laser ionization.But the instantaneous acceleration and deceleration effect will dominant when the laser i onization generates a large number of fragment ions.The numerical simulation of voltage undulation in electrical field is consistent with the experimental values,and also supports the deduction.