“…Electron bombardment was used by Nier (9) to make the first isotopic measurements of Os, and Hirt et al (10) subsequently used the technique to examine Os isotopes in geologic materials with high concentrations of Os. The technique was later refined for making measurements of microgram quantities of Os (11). Much greater sensitivities have been achieved with the ion probe (3,4,12,13), laser microprobe mass analyzer (LAMMA) (14,15), accelerator mass spectrometer (16), and inductively coupled plasma source mass spectrometer (ICPMS) (17).…”