ANALYSIS AND ELIMINATION OF SYSTEMATIC-ERRORS ORIGINATING FROM COULOMB MUTUAL INTERACTION AND IMAGE CHARGE IN FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE PRECISE MASS DIFFERENCE MEASUREMENTS
ANALYSIS AND ELIMINATION OF SYSTEMATIC-ERRORS ORIGINATING FROM COULOMB MUTUAL INTERACTION AND IMAGE CHARGE IN FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE PRECISE MASS DIFFERENCE MEASUREMENTS
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DOI：
10.1016/1044-0305(93)87003-u
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发表时间：
1993-11-01
影响因子：
3.2
通讯作者：
NIKOLAEV, EN
中科院分区：
文献类型：
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作者：
GORSHKOV, MV;MARSHALL, AG;NIKOLAEV, EN
通过分析推导并通过实验测量了两种不同质荷比（但离子回旋轨道半径相等）的离子之间库仑介导的相互作用对其傅里叶变换离子回旋共振（FT/ICR）质谱频率差的影响。对于圆柱形离子陷阱，离子包在理论上被建模为无限延伸的电荷线，并且计算由于线电荷之间的直接库仑斥力以及每个线电荷在陷阱电极上感应的图像电荷而产生的力对回旋加速器频率差的贡献。一个引人注目的理论预测是，质量双峰中离子之间相互库仑排斥对 ICR 频率差的影响可以通过镜像电荷效应来补偿。因此，存在一个最佳的（可计算的）离子回旋轨道半径，在该半径处，两个不同质荷比的离子之间测量的回旋加速器轨道频率差与质量双峰的两个组分之间的相互库仑介导的相互作用无关！此外，如果两个质量双峰组分离子以相等的数量存在，则测量的离子回旋加速器轨道频率差也与两种离子之间的所有库仑介导的相互作用无关！因此，通过适当控制 ICR 轨道半径和/或通过以各种相对丰度比进行测量并外推到两个质量双峰组分的相对丰度相等，实际上可以消除通过 FT/ICR 质谱测量质量双峰中质量差的单个最大系统误差。我们报告了两种不同质量双峰的实验测试和这些预测的验证：He-3+/H-3+（4.7 特斯拉的圆柱形陷阱）和 (CH2+)-C-12-H-1/N-14+（7.0 特斯拉的立方陷阱）。根据后者的测量，我们确定氮原子的质量为 m(N-14) = 14.003 074 014(19) u。
The effect of mutual Coulomb-mediated interactions between ions of two different mass-to-charge ratios (but equal ion cyclotron orbital radii) on their Fourier transform ion cyclotron resonance (FT/ICR) mass spectral frequency difference is derived analytically and measured experimentally. For a cylindrical ion trap, ion packets are modeled theoretically as infinitely extended lines of charge, and contributions to cyclotron frequency difference due to direct Coulomb repulsion between the line charges as well as the forces arising from image charge induced on the trap electrodes by each line charge are calculated. A striking theoretical prediction is that the effect on ICR frequency difference of mutual Coulomb repulsion between ions in a mass doublet may be compensated by the image-charge effect. As a result, there is an optimal (calculable) ion cyclotron orbital radius at which the measured cyclotron orbital frequency difference between ions of two different mass-to-charge ratios is independent of mutual Coulomb-mediated interactions between the two components of the mass doublet! Moreover, if the two mass-doublet component ions are present in equal numbers, then the measured ion cyclotron orbital frequency difference is also independent of all Coulomb-mediated interactions between the two types of ions! Thus, the single largest systematic error in measurement of mass difference in a mass doublet by FT/ICR mass spectrometry may be virtually eliminated by appropriate control of ICR orbital radius and/or by performing measurements at various relative abundance ratios and extrapolating to equal relative abundance of the two mass-doublet components. We report experimental tests and verification of these predictions for two different mass doublets: He-3+/H-3+ (cylindrical trap at 4.7 Tesla) ana (CH2+)-C-12-H-1/N-14+ (cubic trap at 7.0 Tesla). From the latter measurement, we determine the mass of atomic nitrogen as m(N-14) = 14.003 074 014(19) u.