Reply to "Note on isotope sputtering"

In his note commenting on the ^(92)Mo-^(100)Mo isotopic fractionation results of Weathers et al., Sigmund raises questions about the experimental procedures used in these measurements. Specifically, he suggests that isotopic fractionation effects may be present in the SIMS analysis of the carbon collector foils; and, based on conventional sputtering theory, he further suggests that these effects may be as large as 50% of the fractionation from the molybdenum targets themselves, if only a small fraction of the molybdenum was removed from the foils. He also raises questions about the possible relationship between changes in the yield and fractionation versus ion fluence.