Measurements of scattering of light from layered microspheres

Experimental elastic-scattering characteristics of layered microspheres are reported. Single particles consisting of glass cores coated with glycerine are suspended in an evacuated quadrupole trap, and scattered light intensity is measured at a fixed angle as the glycerine evaporates. The results are compared with those calculated for concentric spheres using the Mie theory. Excellent agreement is obtained for glycerine layers of thickness less than 700 nm. For thicker layers, differences occur that are attributed to the effect of gravity on particle structure.