title: Quantum tunneling of oxygen atoms on very cold surfaces.
abstract: Any evolving system can change state via thermal mechanisms (hopping a barrier) or via quantum tunneling. Most of the time, efficient classical mechanisms dominate at high temperatures. This is why an increase of the temperature can initiate the chemistry. We present here an experimental investigation of O-atom diffusion and reactivity on water ice. We explore the 6-25 K temperature range at submonolayer surface coverages. We derive the diffusion temperature law and observe the transition from quantum to classical diffusion. Despite the high mass of O, quantum tunneling is efficient even at 6 K. As a consequence, the solid-state astrochemistry of cold regions should be reconsidered and should include the possibility of forming larger organic molecules than previously expected.
authors: Université de Cergy Pontoise and Observatoire de Paris, ENS, UPMC, UMR 8112 du CNRS 5, mail Gay Lussac, 95000 Cergy Pontoise cedex, France. marco.minissale@obspm.fr
authors: M
authors: M
authors: Minissale
authors: E
authors: E
authors: Congiu
authors: S
authors: S
authors: Baouche
authors: H
authors: H
authors: Chaabouni
authors: A
authors: A
authors: Moudens
authors: F
authors: F
authors: Dulieu
authors: M
authors: M
authors: Accolla
authors: S
authors: S
authors: Cazaux
authors: G
authors: G
authors: Manicó
authors: V
authors: V
authors: Pirronello