A Nucleogenic particle is a microscopic particle which exist in nature and can be emitted by certain forms of equipment or lifeforms.
On Class-M planets nucleogenic particles are necessary to produce rain, without it a planet would be incapable of producing any rain at all. Some forms of technology are capable off destroying nucleogenic particles. (VOY:"Caretaker")
Nucleogenic particles can also be used as a form of energy and there are also nucleogenic based life forms which emit high levels of anti-matter. (VOY:"Equinox, Part I","Equinox, Part II")
The particles themselves can be detected by means of a scanning device.
Planets with no Nucleogenic particles are classified as a Class H Planet.
Examples: Ocampa, Nimbus III, Tau Cygna V, Rigel XII