Ion sputtering on metal oxides: A source of translationally hot O(3P J) atoms for chemical studies above 1 eV

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Abstract
A novel technique is described for generation of translationally ‘‘hot’’ oxygen atoms that can be used for chemical studies. These atoms are produced through ion sputtering on Ta2 O5 targets. Mass‐resolved beams of noble gas ions in the kilovolt energy range are generated for this purpose using a 150‐cm isotope separator. The technique can yield fluxes of oxygen atoms in the range of 1015 –1016 atoms cm−2 s−1 from a 40‐keV argon ion beam with 15‐μA intensity. The sputtered atoms are predominantly neutral and reside exclusively in their 3PJ ground electronic state upon ejection. Translational energy profiles, measured for an incident ion beam angle of 30° from the surface normal, were found to be similar in both the forward and backward scattered directions at a 60° angle from the surface normal. These distributions peaked at about 7 eV, but extended beyond 20 eV. Theoretical calculations using a modified Thompson model yielded a similar distribution at this angle. This suggests that kilovolt ion sputtering on Ta2 O5 proceeds predominantly through a collision cascade mechanism. The energy range provided by this technique opens up a new area of hot‐atom chemistry for oxygen atoms that has been relatively unexplored until now because of the lack of methods for their generation.