Relative humidity anneal effect on hygroscopicity of aerosol particles studied by rapid-scan FTIR-ATR spectroscopy

Rapid-scan Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy was employed to study the effect of the relative humidity anneal on the hygroscopicity of NaCl, NaNO₃ and NaClO₄ aerosol particles. The annealed NaCl, NaNO₃ and NaClO₄ particles deliquesced at the relative humidity of ∼83%, ∼87% and ∼48%, respectively, which are much higher than the deliquescence relative humidity of the unannealed particles. The annealing of the particles was suggested to reduce the surface defects, and thereby delayed the deliquescence relative humidity of hygroscopic aerosol particles, which should be a ubiquitous process in the atmosphere.