Measurements of polyatomic molecule formation on an icy grain analog using fast atoms

Measurements are reported for production of CO2 resulting from the impact of a monoenergetic O(P-3) beam upon a surface cooled to 4.8 K and covered with a CO ice. Using temperature-programmed desorption and mass spectrometer detection, one clearly detects increasing amounts of CO2 formation with O(P-3) energies of 2, 5, 10, and 14 eV. This is a measurement of polyatomic molecule formation on a surface in a new regime using superthermal atoms. The chosen surface coverage, surface temperature, and superthermal atom energy simulate conditions in shock-heated circumstellar and interstellar regions.