Storage and light scattering of microparticles in a ring-type electrodynamic trap

We employ a Paul-Straubel ring-type electrodynamic trap for studies of single microparticles. Such a trap provides ready access for laser beams to a stored species and is especially suited for scattering and spectroscopic studies of fine particles. We derive the pseudopotential for such a trap and determine the stability regions for confinement of charged particles considering also the viscous force of a buffer medium and the force of gravity. The dynamics of microparticles in such a trap is numerically simulated. The diffraction pattern of light scattered on a polystyrene particle of about $10μm$ diameter was registered. For measuring Raman spectra from a single dipicolinic acid microparticle, we used excitation at $488nm$ and detection with a fiber optics spectrometer. To improve the collection of light, the trap with the stored particle was placed inside an elliptical mirror.