ICR vs NMR

Vardan Martikyan

Ion Cyclotron Resonance (ICR)

Ion cyclotron, referred to as IC or more precisely (2D FT-ICR MS that is 2 Dimensional Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry), is an experimental technique designed for the measurement of the masses of ions. One of the applications consists of getting information about the product ions created due to collisions of reactant ions and molecules.

Perhaps, for better understanding, it makes sense to explain the meaning of these words, which speak quite a lot about themselves. Fourier Transform is a mathematical tool used to pass from spatial domain to frequency domain. This passage is required to achieve the final goal, namely the acquisition of ions mass spectrum. Ions cycle in a cell and can be put in resonance with the frequency of the external electric field and be better excited. The final aim is to obtain ions mass spectrum.

Nuclear Magnetic Resonance (NMR)

In NMR (nuclear magnetic resonance) instead of cyclotron frequencies of ions, one deals with intrinsic Larmor frequencies of nuclei. NMR is a topic of interest, particularly for quantum computation. Spins of nuclei, which one can imagine as an ensemble of magnetic arrows if controlled efficiently, can serve as a basis (qubits) for quantum computation.

Magic connection between ICR and NMR

Hopefully, it turns out that there is a magic connection between ICR and NMR, which has been proved scientifically. It states that the optimal field (optimal, e.g. in the sense of minimum applied energy) designed for the excitation of the ions in the cell can be equally well applied for the control of spin systems in NMR (flip of spins shown in the video).

The experiment

At first, the fragmented ions are injected into the cell and subjected to the external homogenous constant magnetic field. Then, while the ions circulate under the influence of the magnetic field, we apply a voltage difference on the two conducting plates creating an external homogenous time-varying electric field. This electric field forces the ions against the conducting plates. The enlargement of ions displacement, in turn, redistributes the charge in plates generating an electric current, which can be detected and amplified. Fourier Transform of the electric current resolves the cyclotron frequencies and masses of the ions.