The Formation of Clusters with Reactive Species Precursors to Aerosol Formation in the Ammonia—Sulfur Dioxide System

Abstract

Reactions between ammonia and sulfur dioxide are known to form aerosols, but no information on the precursors to particle formation are available in the literature. Herein, the first results on the formation of clusters containing both ammonia and sulfur dioxide are presented. Clusters produced by expansion through a dual nozzle into vacuum have been investigated using a molecular beam mass spectrometer technique. Interestingly, under similar expansion conditions, NH₃ incorporation into SO₂ clusters is more extensive than SO₂ into NH₃ clusters. In contrast to findings from the stoichiometry of the solid precipitate of the aerosol, the cluster distributions fail to reveal clusters of any stoichiometry as particularly abundant or stable, except for NH⁺ ₄·NH₃·SO₂.