Sputtering yields for different ions and materials at low ion energies have a similar energy dependence. Due to this similarity, yield data can be characterized by a normalized energy function and two parameters for each ion target combination. One of these parameters is the threshold energy. An energy scaling can be based on this parameter. The other parameter is a multiplication factor. Both parameters depend mainly on the ion and target mass M1 and M2 and on the surface binding energy EB. An analytic expression for the normalized functions and both the parameters is given. This empirical relation also allows an estimate of unknown sputtering data, if M1, M2, and EB are noted. A physical interpretation of the empirical relation is given for the case M1≪M2, as in this case special collision processes which dominate the sputtering can be identified.

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To test the suggestion that an enhancement of sputtering occurs in very dense collision cascades, the sputtering yield per atom was compared for atomic and molecular ions. In all cases tested, the yield per atom was higher for the molecular ions. This effect is the more pronounced the heavier the projectile and the target. In the molecular cases the overlapping cascades have higher energy densities than those initiated by the atomic ions; our results, therefore, support the suggestion of a sputtering enhancement in dense cascades.

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The sputtering yields of molybdenum and gold for H+, D+, 3He+, and 4He+ ion irradiation at normal incidence with large irradiation doses have been measured for energies between 150 eV and 20 keV. The yields were determined from the weight loss of the targets. The sputtering yields are strongly influenced by threshold effects for energies below ∼10 keV. It is found that the experimental yields can be described by a yield formula with an energy parameter E′=E/Eth, where Eth is a theoretical threshold energy.