mass spectrum

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

• noun A pattern of charged atoms, molecules, or isotopes formed when a mass spectroscope distributes them by mass and records them electronically or photographically as a spectrum.

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

• noun The output of a mass spectrometer

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

• noun a distribution of ions as shown by a mass spectrograph or a mass spectrometer