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:
“... in the happy laughter of a theatre audience one can get the most immediate and numerically impressive guarantee that there is nothing in one’s mind which is not familiar to the mass of persons living at the time.”
—Rebecca West (1892–1983)