放射性炭素年代測定法の基礎 : 加速器質量分析法に重点をおいて  [in Japanese] Fundamentals of radiocarbon dating : With accelerator mass spectrometry  [in Japanese]

The fundamentals of radiocarbon (^<14>C) dating, i.e., the principles, basic assumptions, equipment used, sample preparation methods, and the reliability of ^<14>C ages, are described in this article. Radiocarbon dating was initiated in 1947 by W.F. Libby, who measured the β-rays produced by disintegration of ^<14>C. Since then considerable progress has been made in the techniques of detecting low-energy β-rays, as well as in basic research on the distribution of natural ^<14>C, and radiocarbon dating has become one of the most reliable methods for estimating the ages of archeological and geological samples. A new technique of ^<14>C dating, accelerator mass spectrometry (AMS), has developed since 1977. In stead of β-ray counting, actual ions of ^<14>C produced from acarbon sample are identified and counted, using a small electrostatic tandem accelerator and a heavy ion detector. The age of a sample can be measured by the AMS method using only a few milligrams of carbon, in a measurement lasting for 3-5 hours. Errors in the AMS measurement are approximately about equal to or smaller than those for traditional radio activity measurements. The maximum age measurable with the new method has been extended to ca. 60000 y BP. Radiocarbon dating with the AMS method is explained and compared with traditional methods. Sample preparation methods are also discussed. The relationship of the ^<14>C age of a sample and its calendar age is also discussed.