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Updated: Feb 8, 2026

Fluorescence Lifetime Imaging of Molecular Rotors in Living Cells
Published on: February 9, 2012
Gas-induced friction and diffusion of rigid rotors
Lukas Martinetz1, Klaus Hornberger1, Benjamin A Stickler1
1Faculty of Physics, University of Duisburg-Essen, Lotharstraße 1, 47048 Duisburg, Germany.
Abstract:
We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.
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