Ionization

(noun) the condition of being dissociated into ions (as by heat or radiation or chemical reaction or electrical discharge). Synonyms: ionization, ionisation. Example: "The ionization of a gas."

(noun) the process of ionizing; the formation of ions by separating atoms or molecules or radicals or by adding or subtracting electrons from atoms by strong electric fields in a gas. Synonyms: ionization, ionisation.