Harpooning in Surface Scattering:O2−Formation in Collisions ofO2+from Ag(111)

Harpooning transitions or long-range electron jumps have been observed in collisions of ${\mathrm{O}}_2^{+}$ at 100-300 eV from Ag(111) leading to negative molecular ${\mathrm{O}}_2^{-}$ ions. It is demonstrated that the ions are formed in nonviolent collisions and with reasonable probability. The origin and relevance of these harpooning transitions are discussed.