излучение

Noun

 * 1) radiation, emanation

Usage notes
Излуче́ние is the neutral term for "radiation." For example, an object may "излучать тепло" (radiate heat).

Радиация is specifically ionizing radiation (ионизи́рующее излуче́ние) - the harmful form of radiation whereby emitted particles have sufficient energy to strip electrons from atoms or molecules.