line spectrum

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A spectrum produced by a luminous gas or vapor and appearing as distinct lines characteristic of the various elements constituting the gas.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics A spectrum, typically produced by a luminous gas, that consists of separate lines typical of particular elements

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a spectrum in which energy is concentrated at particular wavelengths; produced by excited atoms and ions as they fall back to a lower energy level