Douglas Don J, Polyakov A, Konenkov Nikolai V
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
Physical and Mathematical Department, Ryazan State University, Ryazan, Svoboda 46, 390000, Russia.
Eur J Mass Spectrom (Chichester). 2014;20(3):207-14. doi: 10.1255/ejms.1278.
Trajectory calculations are used to model a mass filter based on the radiofrequency (rf)-only operation of a linear quadrupole with resonant quadrupole excitation of ions (resonant excitation applied with the same spatial electric field as the main quadrupole rf field). Ions are not trapped, but pass continuously through the quadrupole. Excited ions gain axial kinetic energy in the fringe field at the quadrupole exit, overcome a stopping potential and are transmitted to an external detector. No quadrupole direct current is required, unlike conventional operation at the tip of the first stability diagram. Quadrupole excitation can be applied with amplitude or frequency modulation of the main rf voltage, or with an auxiliary excitation voltage. All three methods give the same mass resolution. The mass resolution, R, is given by R ≈ 0.5q(dβ/dq)n where q is a Mathieu parameter, β(q), determines the frequency of ion oscillation and n is the number of cycles of the rf field experienced by an ion, determined by the flight time through the quadrupole. A disadvantage of this mode of operation is that the flight times of the ions and the excitation amplitudes or modulation depths need to be synchronized.
轨迹计算用于基于线性四极杆仅射频（rf）操作对质量过滤器进行建模，其中离子采用共振四极激发（施加与主四极rf场相同空间电场的共振激发）。离子不被捕获，而是连续通过四极杆。被激发的离子在四极杆出口的边缘场中获得轴向动能，克服截止电位并被传输到外部探测器。与在第一稳定图顶端的传统操作不同，不需要四极直流电流。四极激发可以通过主rf电压的幅度或频率调制，或者通过辅助激发电压来施加。所有三种方法都给出相同的质量分辨率。质量分辨率R由R≈0.5q(dβ/dq)n给出，其中q是一个马蒂厄参数，β(q)决定离子振荡频率，n是离子经历的rf场周期数，由通过四极杆的飞行时间确定。这种操作模式的一个缺点是离子的飞行时间与激发幅度或调制深度需要同步。
