Coupling of X-Ray Scattering and Spectroscopy for Oleic Acid Aerosols*

Aerosols are important atmospheric components, for example contributing to cloud formation and impacting human health. Oleic acid provides an atmospherically relevant prototypic system for examining aerosol structures and reactions. We present a novel use of resonant soft X-Ray scattering (RSoXS), coupled to synchrotron X-Ray spectroscopic measurements within the same instrument, to examine oleic acid aerosols before and after ozonation.

X-Ray spectroscopies provide sensitivity to chemical composition and bonding environments; X-Ray scattering provides further structural information. Specifically, RSoXS leverages the tuning of X-Ray photon energy to allow structural measurements with chemical sensitivity. For example, we couple spectroscopic measurements demonstrating the destruction of the carbon-carbon double bond in oleic acid by ozone with RSoXS measurements which confirm the resultant shrinkage of the aerosols, likely due to the loss of volatile products. Structural rearrangement within the aerosol droplets following the reaction is also expected and can be detected through RSoXS. Joint measurement of structure and chemical properties of aerosols offers a novel probe into their behavior.