Journal of Chemical Physics, Vol.107, No.2, 355-362, 1997
Light-Scattering Properties of Paramagnetic Particles
We present an experimental study of light scattering properties of paramagnetic particles.:To account for the magnetic dipole radiation and the Brownian motion of the particles in a thermal equilibrium solution, we calculate the scattering intensity and its auto-correlation function g(t), Experimentally, we examine the scattering properties of the paramagnetic particles and compare the results with those from isotropic and anisotropic dielectric particles. The experiment verifies the calculation and reveals that the magnetic dipole radiation of the paramagnetic particles is unusually large and equals to approximately 1/3 of the electric dipole radiation of the particles. Dynamic light scattering measurements show that the measured g(t) for the depolarized scattering is strongly influenced by the size distribution of the particles. This is because the large paramagnetic particles tend to have more magnetite content and hence weigh more in the depolarized scattering. With a simple sedimentation method, we are able to separate the particles of different sizes and obtain relatively monodispersed scattering samples : These samples give the expected translational and rotational diffusion constants of the particles.