Ion cyclotron resonance is a phenomenon related to the movement of
ions in a
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
. It is used for accelerating ions in a
cyclotron, and for measuring the masses of an ionized analyte in
mass spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...
, particularly with
Fourier transform ion cyclotron resonance mass spectrometers. It can also be used to follow the
kinetics of chemical reactions in a dilute gas mixture, provided these involve charged species.
Definition of the resonant frequency
An ion in a static and uniform magnetic field will move in a circle due to the
Lorentz force
In physics (specifically in electromagnetism) the Lorentz force (or electromagnetic force) is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge moving with a velocity in an elect ...
. The
angular frequency
In physics, angular frequency "''ω''" (also referred to by the terms angular speed, circular frequency, orbital frequency, radian frequency, and pulsatance) is a scalar measure of rotation rate. It refers to the angular displacement per unit tim ...
of this ''cyclotron motion'' for a given magnetic field strength ''B'' is given by
:
where ''z'' is the number of positive or negative charges of the ion, ''e'' is the
elementary charge
The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a fundame ...
and ''m'' is the mass of the ion. An electric excitation signal having a frequency ''f'' will therefore resonate with ions having a mass-to-charge ratio ''m/z'' given by
:
The circular motion may be superimposed with a uniform axial motion, resulting in a
helix, or with a uniform motion perpendicular to the field (e.g., in the presence of an electrical or gravitational field) resulting in a
cycloid.
Ion cyclotron resonance heating
Ion cyclotron resonance heating (or ICRH) is a technique in which
electromagnetic waves
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) lig ...
with frequencies corresponding to the ion cyclotron frequency is used to heat up a
plasma
Plasma or plasm may refer to:
Science
* Plasma (physics), one of the four fundamental states of matter
* Plasma (mineral), a green translucent silica mineral
* Quark–gluon plasma, a state of matter in quantum chromodynamics
Biology
* Blood pla ...
. The ions in the plasma absorb the electromagnetic radiation and as a result of this, increase in
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
. This technique is commonly used in the heating of
tokamak plasmas.
In the solar wind
On March 8, 2013, NASA released an article according to which ion cyclotron waves were identified by its solar probe spacecraft called WIND as the main cause for the heating of the
solar wind as it rises from the sun's surface. Before this discovery, it was unclear why the solar wind particles would heat up instead of cool down, when speeding away from the sun's surface.
See also
*
Cyclotron resonance
Cyclotron resonance describes the interaction of external forces with charged particles experiencing a magnetic field, thus already moving on a circular path. It is named after the cyclotron, a cyclic particle accelerator that utilizes an oscillati ...
*
Electron cyclotron resonance
References
Condensed matter physics
Electric and magnetic fields in matter
Ion source
Scientific techniques
Plasma physics
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