Gas−Surface Chemical Reactions at High Collision Energies?
Most gas−surface chemical reactions occur via reaction of adsorbed species to form a thermal-energy (kT) product; however, some instances exist where an energetic projectile directly reacts with an adsorbate in a single-collision event to form a hyperthermal product (with a kinetic energy of a few eV). Here we show for the first time that 30−300 eV F^+ bombardment of fluorinated Ag and Si surfaces produces "ultrafast" F_2^− products with exit energies of up to 90 eV via a multistep direct-reaction mechanism. Experiments conclusively show that the projectile F atom ends up in the fast molecular product despite the fact that the impact energy is far greater than typical bond energies.
Additional Information© 2009 American Chemical Society. Received October 3, 2008. Publication Date (Web): January 20, 2009. This study was based on work supported by the National Science Foundation under Grant CTS-0613981. Applied Materials, Inc. donated equipment essential for the experiments. Supporting Information: Details of MD and DFT calculations. This material is available free of charge via the Internet at http://pubs.acs.org.
Supplemental Material - Gordonja807672n_si_001.pdf