Radiative forces on dust particles in circumstellar disks

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Radiative forces influence the dynamics of dust particles in circumstellar disks as soon as they become optically thin. Radiation pressure has long been recognized as such a force, however, current disk models implement this force by approximating the dust grains as spheres. While there are a few theoretical works on radiation pressure on non-spherical particles, experimental data of the radiation pressure force on particles with realistic shapes and sizes are missing. The knowledge of the effect of photophoresis, a force exerted on illuminated particles by surrounding gas molecules, is even poorer in this context. The aim of this project is to gain experimental data on the radiation pressure and photophoretic forces on irregularly shaped dust particles of various sizes, forms, and compositions. The application of a previously developed setup for radiation pressure measurements with single particles allows for studying the dependence on the incident wavelength and the particle orientation, and for quantifying the transverse force component. The role of photophoresis for the radial migration of dust in circumstellar disks, the formation of dust rings, and the composition of bodies formed in the outer regions of the disk will be investigated by single particle measurements with a new setup using a quasi-electrostatic particle trap.