ELECTRON-EMISSION FOR IMPACT OF SLOW FULLERENE IONS ON CLEAN GOLD

Electron emission for impact of singly and multiply charged fullerene ions C-n(q+) (15 less than or equal to n less than or equal to 60; 1 l ess than or equal to q less than or equal to 5) on atomically clean po lycrystalline gold has studied at impact energies far from below thres hold up to 250 eV/amu by measuring the number statistics of emitted el ectrons, from which accurate absolute total electron yields have been determined. In contrast to impact of atomic ions the fullerene charge q apparently has no influence on the total electron yield, ie. no pote ntial emission takes place. There is also no clear threshold for the e lectron emission which becomes measurable already around 10 eV/amu, ab ove which it rises faster than linear with the ion impact velocity. Is otachic C-n(q+) ions cause electron yields in direct proportion to the ir size n, with 250 eV/amu C-60(q+) producing on average more than 25 electrons. These results are tentatively explained by assuming that ei ther the fullerene ions are completey shattered at the gold surface an d individual carbon atoms produce kinetic emission, or electrons origi nate from thermionic emission of projectiles and their fragments heate d up in the surface collision.