n. (Elec. Chem.) the process of converting neutral atoms or molecules into ions. The process may occur by dissolving an ionic substance in a dissociating solvent, such as water, or by adding or subtracting an electron to or from an atom or molecule. The latter process occurs, for example, in an electron beam in a mass spectrometer and by interaction of substances with ionizing radiation. [ PJC ]

v. i. 1. (Physics, Chemistry) to dissociate into ions, as by dissolution in water or another polar solvent. [ WordNet 1.5 ]

v. t. [ imp. & p. p. Ionized p. pr. & vb. n. Ionizing ] (Physics, Chemistry) To convert (an atom or molecule) into ions, e. g. by dissolving in water, by reaction with acid or alkali, or by interaction with ionizing radiation. See ionization. [ Webster 1913 Suppl. +PJC ]

adj. converted totally or partly into ions. Opposite of nonionized and unionized. [ WordNet 1.5 ]

n. rays of rapidly moving subatomic particles, x-reys, or gamma rays, sufficiently energetic to cause ionization when absorbed by matter. Such radiation is emitted by radioactive elements, or may be generated by highly energetic physical processes, as in stars. When absorbed by living tissue, ionizing radiation can cause mutation, cellular damage, or death. [ PJC ]