Highly charged ions (HCI) are
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s in very high charge states due to the loss of many or most of their bound
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no ...
s by energetic collisions or high-energy
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...
absorption. Examples are 13-fold ionized iron, or Fe XIV in
spectroscopic notation
Spectroscopic notation provides a way to specify atomic ionization states, atomic orbitals, and molecular orbitals.
Ionization states
Spectroscopists customarily refer to the spectrum arising from a given ionization state of a given element by ...
, found in the
Sun's corona
A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma.
The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total so ...
, or ''naked'' uranium, (U XCIII in spectroscopic notation), bare all bound electrons, which requires very high energy for its production. HCI are found in
stellar corona, in
active galactic nuclei
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...
, in
supernova remnant
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...
s, and in
accretion disks. Most of the visible matter found in the universe consists of highly charged ions. High temperature
plasmas used for
nuclear fusion
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manife ...
energy research also contain HCI generated by the plasma-wall interaction (see
Tokamak
A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being ...
). In the laboratory, HCI are investigated by means of heavy ion
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
s and
electron beam ion traps.
They might have applications in improving
atomic clocks
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...
, advances in
quantum computing, and more accurate measurement of
fundamental physical constants.
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References
{{reflist, refs=
[{{cite web , url=https://jqi.umd.edu/news/highly-charged-ions , title=Highly-Charged Ions , author= , date=July 17, 2014 , website=Joint Quantum Institute , publisher=University of Maryland , access-date=2 December 2019 , quote=]
Atomic physics
Astrophysics