Coincidence counting for the study of hydrocarbon ion desorption in plasma desorption mass spectrometry

Abstract

Abstract-coincidence counting techniques have been used in conjunction with time-of-flight mass spectrometry (TOF-MS) to study the impact of MeV/amu ions on surfaces. Several samples were studied including Au metal and a series of polymers. The results are consistent with a Coulomb explosion model for the secondary ion desorption in plasma desorption mass spectrometry. Correlations were observed between the emission of H+ and the emission of certain hydrocarbon ions from the polymer samples. These correlations indicate a chemical relation in the formation of H+ and other hydrocarbon ions and imply that low mass hydrocarbon ions are formed close to the center of the impact site during the collision of primary ion with the sample. Also, we have shown that the coincidence data contains information about the structure of the samples and that with coincidence counting, an estimate of the yield of secondary ions can be obtained without knowledge of how many primary ions strike the surface.