Predictions and detection of the “accommodation” forces on Janus particles subjected to directed radiation in a rarefied gas

The results of theoretical and experimental study of so-called “accommodation” forces acting on particles with artificial asymmetry of surface properties in rarefied gas in the directed radiation field are presented. The gas-kinetic theory of phenomenon in the free-molecular regime for some different types of boundary conditions of gas-surface interactions is developed. The theory predicts appearance of the unusual force caused by the difference of the normal momentum accommodation coefficients on hemispheres of considered model Janus particle. The measurements conducted by the experimental technique with macroparticles have confirmed the existence of the accommodation forces affecting a particle together with the forces of radiometric photophoresis. The experimental results for the system “steel particle–helium” are in good agreement with theoretical predictions, and the ratio of the “accommodation” forces to the photophoretic force does not exceed 3%. The estimations show that the “accommodation” forces can be comparable in some cases with the radiometric photophoretic forces for micron-sized particles in stratosphere, but do not exceed the gravity force. The action of “accommodation” forces, in our opinion, is not capable to provide effective vertical transport of aerosol particles against gravity at stratospheric altitudes.

► The “accommodation” force (AF) on particle with surface asymmetry in rarefied gas.
► The gas-kinetic theory of AF in the free-molecular regime is presented.
► Experiments with model Janus-macroparticles have confirmed the existence of AF.
► AF is not capable to provide transport of aerosols against gravity in stratosphere.