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Measurement of Partial Pressure at Vacuum Conditions
Published in Igor Bello, Vacuum and Ultravacuum, 2017
Ion cyclotron resonance mass spectrometry (ICR MS) is an instrumental technique to analyze a molecular system with high molecular masses and extreme mass resolution. The technique enables us to analyze large biological macromolecules1061,1062 with high resolution. In respect of trapping ions, the technique carries features of omegatrons, but it is mastered with different ion excitation and advanced signal processing. Ions perform cyclotron motion in crossed high-frequency electric field and strong magnetic field (up to 25 T).1063 The trapped resonance ions oscillate. Ion oscillation induces electric mirror signals in pickup electrodes. The signal is then mathematically processed using Fourier transform analysis with acquisition of mirror signals.
Characterization of harmonics and multi-charged peaks obtained by Fourier transform ion cyclotron resonance mass spectrometry
Published in Instrumentation Science & Technology, 2018
Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) is characterized by high resolution, high-quality detection limit, high scanning speed, wide dynamic range, high quality accuracy, and other technical advantages and is therefore widely used in forensic identification, metabonomics, natural products, and food science.[1234567891011121314151617] FTICR MS is based on the principle that charged particles gyrate with a cyclotron frequency that is proportional to their charge and mass, that is, m/q:ωc = qB/m. Although the ion motion equation is linear, the ion cyclotron resonance (ICR) cell has a nonlinear response, which produces a transient signal, including frequency, mass spectrum, and some additional peaks. The peaks that correspond to the harmonics of the fundamental frequencies may appear in the spectrum.[18] Specifically, if a signal is periodic with frequency f, then the only frequencies comprising the signal are integer multiples of f: f, 2f, 3f, 4f, and so on. These frequencies are called harmonics.[19]