Ion nucleation as a detector: application of REMPI to generate selected ions in supersaturated vapors

Resonance enhanced multiphoton ionization (REMPI) of aromatic molecules present in a small concentration within a supersaturated host vapor is demonstrated. The method is applied to the study of ion nucleation in supersaturated vapors of methanol, acetonitrile and nonane induced by the molecular ions of benzene, toluene, and p-xylene. With this method it is now possible to selectively and unambiguously generate specific ions of interest and study their nucleating behavior. Furthermore, the selectivity of REMPI combined with the amplification and detection capabilities of nucleation and growth offer valuable analytical features for the identification of trace components in supersaturated vapors.