WordNet sense 1 (a group of nearly parallel lines of electromagnetic radiation):

beam, electron beam

WordNet sense 2 (a column of light (as from a beacon)):

irradiation, shaft, beam of light, light beam, ray of light, shaft of light

WordNet sense 3 (the syllable naming the second (supertonic) note of any major scale in solmization):

re, re

WordNet sense 4 (extend or spread outward from a center or focus or inward towards a center):

radiate

WordNet sense 5 (expose to radiation):

irradiate