An enhanced, dual wavelength light scattering technique to investigate the surface properties of single MF particles is presented. By using a core-shell approach, it is possible to map the optical properties of the particle to the surface morphology, and thus the surface structure becomes accessible in situ. Using 1 % and 5 % of admixed oxygen in the argon discharge, the particle surface can be modified by a controlled etching process. The measurements show a saturated surface modification of the upper ≈80 nm that dominates the interaction between particle and illumination laser, while an analysis of the levitation height of differently modified particles shows a clear effect of the surface morphology on the particle charge. The findings emphasize the significance of the particle morphology for the overall plasma–particle interaction.
Wohlfahrt et al. (2026) studied this question.