Wiktionary
emission lines
n. (plural of emission line English)
Usage examples of "emission lines".
Careful analysis showed emission lines from silicon, carbon, iron.
Then came the shock that time and time again the sources turned out to be quasars, often showing other attributes of matter in an excited state, such as X-ray emissions and optical emission lines of highly energized atoms.
Flows of glowing matter popped suddenly in and out of visibility, as the Doppler effect took the emission lines of the gas into and then out of coincidence with the spectral line being used for observation.