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 convent ...

s in very high charge states due to the loss of many or most of their bound

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

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 particles that can ...

absorption. Examples are 13-fold ionized

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

, 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 In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's atmosphere. It is a hot but relatively dim region of plasma populated by intermittent coronal structures such as prominences, coronal loops, and helmet streamers. ...

, or ''naked''

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

, (U XCIII in spectroscopic notation), which is bare of all bound electrons, and which requires very high energy for its production. HCI are found in

stellar corona In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's Stellar atmosphere, atmosphere. It is a hot but relatively luminosity, dim region of Plasma (physics), plasma populated by intermittent coronal structures such as so ...

, in

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

, 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 disk An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and ...

s. Most of the visible matter found in the

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

consists of highly charged ions. High temperature plasmas used for

nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...

energy research also contain HCI generated by the plasma-wall interaction (see

Tokamak A tokamak (; ) is a device which uses a powerful magnetic field generated by external magnets to confine plasma (physics), plasma in the shape of an axially symmetrical torus. The tokamak is one of several types of magnetic confinement fusi ...

). 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 electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

s and

electron beam ion trap Electron beam ion trap (EBIT) is an electromagnetic bottle that produces and confines highly charged ions. An EBIT uses an electron beam focused with a powerful magnetic field to ionize atoms to high charge states by successive electron impact. ...

s. 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 A quantum computer is a computer that exploits quantum mechanical phenomena. On small scales, physical matter exhibits properties of wave-particle duality, both particles and waves, and quantum computing takes advantage of this behavior using s ...

, and more accurate measurement of fundamental physical constants.

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