Ion cyclotron resonance (ICR) cells provide stability and coherence of ion oscillations in crossed electric and magnetic fields over extended periods of time. Using the Fourier transform enables precise measurements of ion oscillation frequencies. These precisely measured frequencies are converted into highly accurate mass-to-charge ratios of the analyte ions by calibration procedures. In terms of resolution and mass accuracy, Fourier transform ICR mass spectrometry (FT-ICR MS) offers the highest performance of any MS technology. This is reflected in its wide range of applications. However, in the most challenging MS application, for example, imaging, enhancements in the mass accuracy of fluctuating ion fluxes are required to continue advancing the field. One approach is to shift the ion signal power into the peak corresponding to the true cyclotron frequency instead of the reduced cyclotron frequency peak. The benefits of measuring the true cyclotron frequency include increased tolerance to electric fields within the ICR cell, which enhances frequency measurement precision. As a result, many attempts to implement this mode of FT-ICR MS operation have occurred. Examples of true cyclotron frequency measurements include detection of magnetron inter-harmonics of the reduced cyclotron frequency (i.e., the sidebands), trapping field-free (i.e., screened) ICR cells, and hyperbolic ICR cells with quadrupolar ion detection. More recently, ICR cells with spatially distributed ion clouds have demonstrated attractive performance characteristics for true cyclotron frequency ion detection. Here, we review the corresponding developments in FT-ICR MS over the past 40 years.

中文翻译：

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真实回旋频率下的傅里叶变换离子回旋共振质谱

离子回旋共振 (ICR) 电池在较长时间内提供交叉电场和磁场中离子振荡的稳定性和相干性。使用傅里叶变换可以精确测量离子振荡频率。这些精确测量的频率通过校准程序转换为分析物离子的高精度质荷比。在分辨率和质量精度方面，傅里叶变换 ICR 质谱 (FT-ICR MS) 提供了所有 MS 技术中最高的性能。这体现在其广泛的应用领域。然而，在最具挑战性的 MS 应用中，例如成像，需要提高波动离子通量的质量精度才能继续推进该领域。一种方法是将离子信号功率转变为对应于真实回旋加速器频率的峰值，而不是降低的回旋加速器频率峰值。测量真实回旋加速器频率的好处包括增加对 ICR 单元内电场的耐受性，从而提高频率测量精度。因此，已经出现了许多实现这种 FT-ICR MS 操作模式的尝试。真正的回旋加速器频率测量的示例包括检测降低的回旋加速器频率（即边带）的磁控管间谐波、捕获无场（即屏蔽）ICR 单元和具有四极离子检测的双曲线 ICR 单元。最近，具有空间分布离子云的 ICR 单元已经展示了真正的回旋加速器频率离子检测的有吸引力的性能特征。这里，