Isobar suppression studies for 99Tc detection using Ion-Laser InterAction Mass Spectrometry (ILIAMS)

Ion-Laser InterAction Mass Spectrometry (ILIAMS) has the potential to discriminate 99Tc against isobaric background caused by stable 99Ru to allow for the detection of environmental 99Tc concentrations (approximate to 107 atoms/L) at low beam energies. As the electron detachment energies for Tc molecules are not available, Ru and Tc suppression for oxide and fluoride molecules using the available laser systems were determined experimentally for the first time. TcF-5 was identified as the most promising anion, as RuF-5 was suppressed by a factor 105 with the 2.33 eV laser while TcF-5 stayed unaffected. Additional Ru suppression in the ion source of another factor 100 was observed. We thus unambiguously identified the 99Tc signal from global fallout in an Austrian peat bog sample. However, no satisfactory suppression of stable 97Mo was achieved, thus hindering the use of the isotopic spike 97Tc for normalizing the detected 99Tc events. Therefore, alternative normalization methods need to be explored.