Highly charged ions (HCI) areions in very high charge states due to the loss of many or most of their boundelectrons by energetic collisions or high-energyphoton absorption. Examples are 13-fold ionizediron,Fe13+
or Fe XIV inspectroscopic notation, found in theSun's corona, ornakeduranium,U92+
(U XCIII in spectroscopic notation), which is bare of all bound electrons, and which requires very high energy for its production. HCI are found instellar corona, inactive galactic nuclei, insupernova remnants, and inaccretion disks. Most of the visible matter found in theuniverse consists of highly charged ions.[1] High temperatureplasmas used fornuclear fusion energy research also contain HCI generated by the plasma-wall interaction (seeTokamak). In the laboratory, HCI are investigated by means of heavy ionparticle accelerators andelectron beam ion traps.[2] They might have applications in improvingatomic clocks, advances inquantum computing, and more accurate measurement offundamental physical constants.[3]