Sulfuric acid and ammonia are likely to be involved in the initial stages of atmospheric new particle formation and growth. Other amines, present in much lower concentrations in the atmosphere, and are expected to interact with sulfuric acid more strongly than ammonia does, leading to a mechanism in which amines displace ammonia in new particles. However, due to a lack of understanding of acid/base interactions in a minimally solvated environment, this process is poorly understood. In this work, charged clusters containing sulfuric acid and ammonia were generated via electrospray ionization and investigated using mass spectrometry and infrared predissociation spectroscopy. Collision-induced dissociation experiments using an ion trap mass spectrometer (Thermo LTQ XL) investigate charging composition of cluster constituents. Clusters containing bisulfate, sulfuric acid, ammonia, and ammonium were also observed on a home built Time-of-Flight (TOF) mass spectrometer. The atmosphere of the electrospray environment on this instrument can be altered by introducing trace vapors, and cluster growth can be monitored. Through manipulation of the ESI solutions and the electrospray environment, ammonia can be substituted by methylamine, dimethylamine, or trimethylamine, and their cluster structures can be probed with infrared spectroscopy.

Amine substitution studies of atmospherically relevant anionic clusters

254th National Meeting (2017)

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