photoionization

[ foh-toh-ahy-uh-nuh-zey-shuh n ]
/ ˌfoʊ toʊˌaɪ ə nəˈzeɪ ʃən /

noun Physics.

the phenomenon in which the absorption of electromagnetic radiation by an atom in a gas induces the atom to emit a bound electron and thereby become ionized.

Origin of photoionization

1910–15; photo- + ionization