title: Attractive optical forces from blackbody radiation.
abstract: Blackbody radiation around hot objects induces ac Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object. We explicitly calculate the resulting attractive blackbody optical dipole force for ground state hydrogen atoms. Surprisingly, this force can surpass the repulsive radiation pressure and actually pull the atoms against the radiation energy flow towards the surface with a force stronger than gravity. We exemplify the dominance of the "blackbody force" over gravity for hydrogen in a cloud of hot dust particles. This overlooked force appears relevant in various astrophysical scenarios, in particular, since analogous results hold for a wide class of other broadband radiation sources.
authors.affiliation: Institute for Theoretical Physics, University of Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Sonnleitner
authors.forename: M
authors.initials: M
authors.lastname: Ritsch-Marte
authors.forename: H
authors.initials: H
authors.lastname: Ritsch
mesh_terms: D003359:Cosmic Radiation; D006358:Hot Temperature; D006859:Hydrogen / Q000737:chemistry; D008962:Models, Theoretical; D055095:Optics and Photonics; D010825:Physics; D013816:Thermodynamics
chemical_list: D006859:Hydrogen