Accelerator technique improves radioisotope dating

Stimulated largely by recent developments in archaeology and the environmental sciences, physical scientists have been giving a good deal of attention to the practical problem of getting better carbon‐14 dates. One particular area of renewed interest is the use of a mass spectrometer to separate the radioactive $C14$ from other carbon isotopes. The $C14$ content could then be measured directly, rather than by counting decays as is done now. The difficulty has been that conventional mass spectrometers are not sufficiently sensitive to detect the small percentages of $C14$ present in typical samples: The $C14$/$C12$ ratio ranges from $1.2×10−12/l$ in contemporary biological samples down to about $3×10−16/l$ in samples older than 70 000 years or so.