S. C. Beu Consulting, 12449 Los Indios Trail, Austin, TX 78729, USA.
J Am Soc Mass Spectrom. 2011 Mar;22(3):591-601. doi: 10.1007/s13361-010-0057-9. Epub 2011 Feb 2.
Radiofrequency (rf) multipole ion guides are widely used to transfer ions through the strong magnetic field gradient between source and analyzer regions of external source Fourier transform ion cyclotron resonance mass spectrometers. Although ion transfer as determined solely by the electric field in a multipole ion guide has been thoroughly studied, transfer influenced by immersion in a strong magnetic field gradient has not been as well characterized. Recent work has indicated that the added magnetic field can have profound effects on ion transfer, ultimately resulting in loss of ions initially contained within the multipole. Those losses result from radial ejection of ions due to transient cyclotron resonance that occurs when ions traverse a region in which the magnetic field results in an effective cyclotron frequency equal to the multipole rf drive frequency divided by the multipole order (multipole order is equal to one-half the number of poles). In this work, we describe the analytical basis for ion resonance in a rf multipole ion guide with superposed static magnetic field and compare with results of numerical trajectory simulations.
射频（rf）多极离子阱广泛用于将离子从外部源傅里叶变换离子回旋共振质谱仪的源区和分析器区之间的强磁场梯度中传输。尽管仅由多极离子阱中的电场决定的离子传输已经得到了彻底的研究，但受浸入强磁场梯度影响的传输尚未得到很好的描述。最近的工作表明，外加磁场会对离子传输产生深远的影响，最终导致最初包含在多极中的离子丢失。这些损失是由于离子在穿过磁场导致有效回旋频率等于多极射频驱动频率除以多极阶（多极阶等于极数的一半）的区域时发生的瞬态回旋共振而导致的径向离子发射引起的。在这项工作中，我们描述了叠加静态磁场的射频多极离子阱中离子共振的分析基础，并与数值轨迹模拟的结果进行了比较。
