Electronic sputtering by swift highly charged ions of nitrogen on amorphous carbon

Electronic sputtering with heavy ions asa function of both electronic energ y loss dE/dx and projectile charge state q was studied at the French heavy ion accelerator GANIL. Amorphous carbon (untreated, and sputter-cleaned and subsequently exposed to nitrogen) was irradiated with swift highly charged ions (Z = 6-73, q = 6-54, energy 6-13 MeV/u) in an ultrahigh vacuum scatte ring chamber. The fluence dependence of ibn-induced electron yields allows to deduce a desorption cross-section a which varies approximately as sigma similar to'(dE/du)(1.65) or sigma similar to q(3.3) for sputter-cleaned amo rphous carbon exposed to nitrogen. This q dependence is close to the cubic charge dependence observed for the emission of H+ secondary ions which are believed to be emitted from the very surface. However, the power law sigma similar to (dE/dx)(1.65), related to the electronic energy loss gives the b est empirical description. The dependence on dE/dx is close to a quadratic one thus rather pointing towards a thermal evaporation-like effect. (C) 200 1 Elsevier Science B.V. All rights reserved.