Mass Spectra
DART produces relatively simple mass spectra, dominated by protonated molecules + in positive-ion mode, or deprotonated molecules - in negative-ion mode. Depending on the nature of the molecule, other species may be formed, such as M+. from polynuclear aromatic hydrocarbons. Fragmentation may occasionally be observed for some molecules. Multiple-charge ions and alkali metal cation aducts are never observed, but addition of ammonia or other "dopants" to the DART gas stream can be used to form single-charge adducts such as + or - for compounds that would not readily form molecular ions or protonated molecules. For example, the explosives nitroglycerin and HMX do not form -, but readily form - if chloride is present.
Read more about this topic: DART Ion Source
Famous quotes containing the word mass:
“There are no fixtures in nature. The universe is fluid and volatile. Permanence is but a word of degrees. Our globe seen by God is a transparent law, not a mass of facts. The law dissolves the fact and holds it fluid.”
—Ralph Waldo Emerson (18031882)