Photophoresis of micrometer-sized particles in the free-molecular regime

The photophoretic force in the free-molecular regime has been calculated for a spherical particle using the Lorenz‐ Mie solution to the electromagnetic field within the particle. The temperature distribution on the surface of the suspended particle is calculated using a finite diAerence method. The eAect of the complex refractive index ma na ik and the normalized size parameter defined as aa 2pa=k on the photophoretic force and particle velocity are also examined. We show that for a 1 solar constant illumination, the photophoretic forces might be as high as 20% of the weight of the particles considered. ” 2001 Published by Elsevier Science Ltd.