The post-ionisation of Pb ions from a molten Sn host field-ion emitter

A tin liquid metal ion source contaminated with led has been studied. From a detailed analysis of the source mass spectra as a function of emission current it is established that while Sn+, Sn++ and Pb+are directly field-evaporated from the liquid surface, Pb++ forms by the post-ionisation of Pb+. Moreover, our results for, the Pb++/Pb+ ratio are in excellent agreement with those of Komuro (1983), obtained with a pure led LMIS.