Accelerator mass spectrometry of 99Tc

FIFIELD, L.K.; CARLING, R.S.; CRESSWELL, R.G.; HAUSLADEN, P.A.; DI TADA, M.L.; DAY, J.P.

BEAM INTERACTIONS WITH MATERIALS AND ATOMS.

Elsevier Science Publishers B.V.

Año: 2000 vol. 168 p. 427 - 436

0168-583X

The measurement of low levels of 99Tc (T 1/2 = 213 ka) by accelerator mass spectrometry (AMS) is reported for the first time. Because there are no stable isotopes of technetium, the 99Tc content of a sample is determined from the ratio of 99Tc to a known trace amount of 103Rh. High-purity aluminium oxide constitutes the bulk of each sample. The contribution from the 99Ru isobar may be quantified and subtracted using 101Ru. In contrast to conventional AMS in which at least one isotope is measured as a beam current, here all three isotopes, 99Tc, 101Ru and 103Rh, are counted ion-by-ion in a propane-filled ionization chamber. This ionization chamber permits partial, but not complete, separation of 99Tc from 99Ru ions. The technique has been validated using a series of standards, as well as a set of five seaweed samples from an inter-laboratory comparison exercise. In addition, the technique has been used to measure the relative intensities of the Tc- and TcOm - (m = 1-4) negative ions from a Cs sputter ion source.