离子在矩形波四极场中的运动与四极场离子阱质谱的数字化操作

矩形波驱动的四极场同样可用于对离子进行质量分析和存储。本文推导了离子在矩形波四极场中的运动规律，并以常用于正弦波四极场的马绍方程参量a,q来表出离子的稳定性。运用赝势阱概念探讨了离子在这种四极场中的本征振动，推导了本征振动频率的近似公式。在理论研究的基础上，提出了数字化离子阱质谱的概念，并运用离子光学模拟，研究了实际离子阱几何结构下的共振出射以及数字化质量扫描的可行性。

Ion Motion in the Rectangular Wave Quadrupole Field and Digital Operation Mode of a Quadrupole Ion Trap Mass Spectrometer

A quadrupole electric field driven by a rectangular wave voltage can be used for mass selective storage and analysis.The ion motion in such an electric field is derived,and the stability of ions is presented in the a q diagram which is commonly used for sinusoidal wave quadrupole mass spectrometry in association with the solution of Mathieu Equation.The pseudo potential well is discussed in an appoximation process that leads to the relation of secular frequency with operation parameters.A scheme of the digital ion trap mass spectrometer is outlined upon the base of the theory.A ion optical simulation was performed to check the theory and to prove the feasibility of the mass scan method for the practical ion trap geometry.