Omicron radiation
Omicron radiation is an energy form which can only be created by certain forms of matter-antimatter reactions, and which can be toxic to certain forms of humanoid life. Extremely rare, omicron particles can be utilized in holography and to replenish antimatter reserves. (; ; ; )

The warp core of the Vissian starship which  encountered in 2153 produced omicron radiation. This necessitated an inoculation be given to Commander Tucker to permit him to visit the Vissians' engineering section. When Tucker asked Doctor Phlox how long the inoculation would last, Phlox responded that it should protect him from omicron radiation for "about twelve years." ()

Later that year, Doctor Phlox was attacked by a member of a mysterious, cybernetic species, and infected with a series of aggressive nanoprobes as part of a process to transform Phlox into a member of this species. Discovering that the nanoprobes' intramolecular processors were vulnerable to omicron particles, Phlox exposed himself to an excessive dose, a process which, while successful, caused Phlox a great amount of discomfort. ()

Also in that year, when attempting to discover a way to disable the organic power cells in Xindi-Reptilian particle rifles, Tucker and Phlox began bombarding them with different forms of radiation, and discovered that omicron radiation caused the cells to reproduce at an accelerated rate. ()

Yaderan holographic technology utilized manipulated omicron particle fields to generate physical objects. in 2370, Lieutenant Jadzia Dax and Constable Odo discovered a colony on a planet in the Gamma Quadrant, all of whose inhabitants where holographic characters created in such a matter, save for one: Rurigan, who utilized the technology to recreate his friends and family after fleeing the Dominion. ()

In 2371, the crew of the  entered a nebula in which they had detected unusually high levels of omicron particles, hoping to collect the particles to provide an additional antimatter reserve. It was eventually determined, however, that the phenomenon was not, in fact, a nebula, but rather an enormous lifeform which utilized omicron particles in its circulatory system. Realizing that they had seriously injured the lifeform upon entering it, Captain Janeway ordered Voyager into the being's wound, allowing the ship, the energy systems of which were compatible with omicron particles, to serve as an energy conduit across the wound, facilitating a regeneration of the damaged tissue. Directing two nucleonic beams fore and aft, parallel to the central axis of the ship, the crew of Voyager were successfully able to heal the lifeform which they had inadvertently wounded. ()

In 2374, Commander Chakotay, Voyagers first officer, detected omicron radiation in the atmosphere of a planet while on a survey mission. Moving in to investigate, Chakotay was shot down by a species called the Vori, who attempted to to conscript him into their conflict against the Kradin, using a series of sophisticated mind control techniques. ()

In 2378, Voyager crewmember Icheb was injured by what appeared to be a weapon of Chokuzan design, his s having been necrotized by a form of omicron radiation. It was later revealed, however, that the Chokuzan who had attacked the vessel on which Icheb was a passenger was actually Q, who was subjecting his son to a test of character by seemingly injuring Icheb, who was his son's best friend. ()

de:Omicronstrahlung
Radiation