Nonlinear effects in sputtering of organic liquids by keV ions

The principal features of the spike probability model are summarized, and calculations based on the model are compared with the keV-ion sputtering data recently obtained from organic liquids. This data, which includes yields for anions of mononucleotides, cations of an organic surfactant, and hydride ions, permits the validity of the spike probability model to be examined over a wider range of both primary particles and impact energies than heretofore possible. It is demonstrated that the nonlinear sputtering effects observed when liquid organics are bombarded by atomic and multiatomic keV ions are described well when energy straggling in the transfer of primary ion energy to the target is used as a basis for calculating the probability of forming energy spikes. This spike probability model accounts for experimental yields in several cases where treatments based solely on mean stopping power are found deficient. Specifically, the model's more complete description seems to be required when, as in the case of intact molecules sputtered from condensed organic phases, spike phenomena predominate.