九大原子核セミナー

2009年3月23日(月) 16:00

講師：Prof. Wolfgang Kretschmer 　(Erlangen Univ., Germany)
演題：The Erlangen AMS facility and its applications to interdisciplinary research

概要 :

Accelerator mass spectrometry (AMS) is an ultrasenstive method for the measurement of isotope ratios of a long lived radioisotope to
a stable isotope (e.g. 14C/12C = 10exp(-12)) with numerous applications in interdisciplinary research. The Erlangen AMS facility,
based on an EN tandem accelerator and a sputter ion source for solid and gaseous samples is well suited for age determination of
materials with carbon content for periods of more than 50.000 years. For archaeology most common samples are charcoal, wood,
textile, paper and bone, but using new preparation methods ancient iron artefacts and lime mortar can be dated by the 14C method.
Some interesting archaeological applications of AMS will be shown, e.g.
the 14C dating of a Persian mummy. Biological applications involve the dating of soil and pollen in peat samples, from a
simultaneous pollen analysis the vegetation history can be deduced. An important topic in environmental research is the origin of
organic compounds in nature. This can be investigated by the determination of the 14C content of the compound, since an
anthropogenic input can be deduced from industrial production via oil and coal which contain no 14C, compounds from biogenic sources
have 14C concentration of living organisms. The problem with this application is the extremely low abundance of compounds of
interest in natural samples, so that after concentration and fraction separation in a gas chromatograph (GC) only carbon masses in
the microgram range are available for AMS measurements. To minimize any carbon contamination we have developed a closed system from
the GC to the gas ion source. With this new facility the 14C content of monochloroacetic acid with carbon masses down to few
microgram can be reliably determined.