title: Collisional dynamics in a gas of molecular super-rotors.
abstract: Recently, femtosecond laser techniques have been developed that are capable of bringing gas molecules to extremely fast rotation in a very short time, while keeping their translational motion relatively slow. Here we study collisional equilibration dynamics of this new state of molecular gases. We show that the route to equilibrium starts with a metastable 'gyroscopic stage' in the course of which the molecules maintain their fast rotation and orientation of the angular momentum through many collisions. The inhibited rotational-translational relaxation is characterized by a persistent anisotropy in the molecular angular distribution, and is manifested in the optical birefringence and anisotropic diffusion in the gas. After a certain induction time, the 'gyroscopic stage' is abruptly terminated by an explosive rotational-translational energy exchange, leading the gas towards the final equilibrium. We illustrate our conclusions by direct molecular dynamics simulation of several gases of linear molecules.
authors.affiliation: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Khodorkovsky
authors.affiliation: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Uri
authors.initials: U
authors.lastname: Steinitz
authors.affiliation: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS (UMR 7583), Université Paris Est Créteil, Université Paris Diderot, Institut Pierre-Simon Laplace, 94010 Créteil, France.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Hartmann
authors.affiliation: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ilya Sh
authors.initials: ISh
authors.lastname: Averbukh