离子阱在不同真空条件下的离子出射方式研究

Ion Emission Mode of Mass Spectrometry under Different Vacuum Conditions

离子阱质谱在质量分析中取得了越来越广泛的应用。在质量分析过程中有多种对离子阱的操作模式,不同操作模式造成了离子的出射方式不同。质谱分析过程中腔室对于真空度的要求较高。基于离子运动理论,通过选取合适的碰撞模型,从10-3 Pa到100 Pa的压强条件下对离子使用不同出射方式进行仿真。探究了不同出射方式下各种条件对质量分辨率的影响。仿真发现:在使用射频电压(radio frequency,RF)扫描和辅助交变(alternating current,AC)电压恒定的电压施加方式时,质量分辨率受到离子碰撞概率和交变电场施加的动能的共同影响。同时施加合适的辅助交变扫描电压可以避免离子提前激发或者弛豫滞后激发,进一步提高分辨率。目前尚未有对这一理论的定量分析。最后通过优化出射方式,仿真实现了在100 Pa的压强下取得220的质量分辨率。相比于边界不稳定出射将质量分辨率提升了185%。

Ion trap mass spectrometry has been widely used in mass analysis.In the process of mass analysis,there are several operation modes for the ion trap,and different operation modes result in different ion emission modes.In the process of mass spectrometry analysis,the chamber has a high requirement for the vacuum.Based on the ion motion theory,by selecting an appropriate collision model,different ion emission modes are simulated from 10^(-3)Pa to 100 Pa.The influence of various conditions on the mass resolution under different emission modes is researched.The simulation shows that when using scanned radio frequency(RF)voltage and voltage application with constant auxiliary alternating current(AC)voltage,the mass resolution is affected by the ion collision probability and the kinetic energy applied by the alternating electric field.At the same time,applying appropriate auxiliary alternating sweeping voltage can avoid the ion excitation in advance or relaxation lag excitation and further improve the resolution.At present,there is no quantitative analysis of this theory.Finally,through the optimization of the emission mode,the simulation realized that the mass resolution of 220 is achieved under the pressure of 100Pa.Compared with the boundary unstable emission mode,the mass resolution was increased by 185%.