Cluster ion beam generation from a wetted needle emitter for organic secondary ion mass spectrometry (organic SIMS) using a protic ionic liquid, propylammonium nitrate

摘要

Rationale: Propylammonium nitrate (PAN, [C3H7NH3][NO3]), a protic ionic liquid, has an active proton in its molecular structure, so that it can promote protonation. In addition, PAN has high aggregability, so that it tends to form large aggregated (or cluster) ions. These features will be desirable for cluster ion beams in secondary ion mass spectrometry (SIMS) of organic materials. The aggregability may enable us to generate a cluster ion beam from a needle tip wetted with PAN by electrospray in vacuum. For these reasons, cluster ion beam generation was investigated using an externally wetted needle emitter.