Light-scattering intensity fluctuations in single aerosol particles during deliquescence

We use the deliquescence of single NaCl- and NaF-particles levitated in an electrodynamic trap to study light-scattering intensity fluctuations. During deliquescence the volume of the solid crystal and the liquid around it can be measured simultaneously with the light-scattering intensity. Such an experiment allows a comparison with numerical simulations of the intensity fluctuations in microdroplets containing inclusions. We find a power-law dependence proportional to the area of the inclusion for inclusions with radii approximately less than half in size of the total radius of the droplet. For larger inclusions this changes to a power law with a proportionality to the radius of the inclusion. A change of 30% in total radius does not change the intensity fluctuations. There seems to be no distinct difference in the behaviour of NaCl and NaF particles, even though the refractive index difference between solid inclusion and liquid host is 0.165 in the former and less than 0.009 in the latter. Furthermore, the fluctuation data of the pure NaCl deliquescence is applied to the ternary NaCl-CaCl2-H2O system and show good agreement with thermodynamic data. (C) 2001 Elsevier Science Ltd. All rights reserved.