Studies of one and two component aerosols using IR/VUV single particle mass spectrometry: Insights into the vaporization process and quantitative limitations

Abstract

This paper presents the studies of one and two component particles using a CO₂ laser for vaporization and VUV ionization in an ion trap mass spectrometer. The degree of fragmentation for a one component system was demonstrated to be a function of CO₂ laser energy. In a two component system, the degree of fragmentation was shown to be a function of the particle composition. This observation indicates that the analysis of mixed particles may be far more complicated than anticipated for a two step process with soft vaporization. In addition to showing that fragmentation is a function of CO₂ laser energy and particle composition, we also show that a key parameter that determines the extent of fragmentation is the energy absorbed by the particle during desorption. The ionization delay profile in a one component system is also shown to be strongly dependent on the vaporization energy. In a two component system, the delay profile is shown to strongly depend on the composition of the particle. The combined data suggest that the key parameter that governs the delay profile is the energy absorbed by the particle during desorption. This finding has implications for potential field measurements. Finally, for a two component system where the absorption crosssections are different, the change in the degree of fragmentation with particle composition resulted in a non-linear dependence of ion signal on composition. This makes any attempt at quantification difficult.