表面電離法による微量Mn同位体の測定

抄録

Mass spectrometric determinations for trace amounts of radioactive ⁵⁴ Mn and ⁵³Mn in the presence of ⁵⁵Mn have been studied. Both ⁵⁴Mn and ⁵³Mn are readily produced by nuclear reactions. Absolute amounts of each isotope could be obtained from the disintegration rate of ⁵⁴Mn and the isotope ratios of ⁵⁴Mn to the others. In order to find suitable experimental conditions in the isotope ratio, measure ments, a commercially available“ carrier-free ⁵⁴Mn” was used as the sample.
The manganese fraction was extracted from the sample containing 10⁷ dpm of ⁵⁴Mn and was puri fied for our mass spectrometric measurements by a wet chemical method. A silica gel method was applied for the solid source surface ionization and a pulse-counting method was improved to measure the extremely weak ion beam current. In one run about 10¹¹ atoms of ⁵⁴Mn could be determined with a high reproducibility in the presence of about 10¹⁴ atoms of ⁵⁵Mn. Furthermore, coexisting ⁵³Mn at the level of 10 ¹⁰ atoms could also be detected with about±10%error.
This method has been applied to determine the production cross-sections of ⁵⁴Mn and ⁵³Mn induced in a cyclotron-irradiated iron target.