Manganese-53: Development of the AMS technique for exposure-age dating applications

The cosmogenic isotope ⁵³Mn is produced by spallation of iron in surface rocks. The long half life of this isotope makes it attractive for use in erosion rate studies in slowly eroding landscapes such as Australia. We describe the development of AMS methods for detection of ⁵³Mn using the 14UD accelerator at the Australian National University. The first step of this development involved the production of ⁵³Mn using a heavy-ion fusion–evaporation reaction to make test standards. Then, the chemistry protocol for isolating ⁵³Mn and reducing the Cr levels, of which ⁵³Cr is a serious interfering isobar, was developed. Lastly we employed a gas-filled magnet which was used to discriminate ⁵³Mn from the intense ⁵³Cr background.