strait lins is a fumcticn of Wie beta enersy of the unimnown isotope and the intercept of the line with the zero abserber represents the relative amount of that isotope present in a mixture. The advantage of thie method lies in ita eppiicability to low counting levels. This .s possible because the lings slope can determined from light acsorbers rather than the heavy absorbe required for Feather analyses. The method is in tentative us for isotope characterization for mixtures of isotopes and sh be applicable to determination of Sr°*/*° ratios. ay ws z ert a“ peree a * mee Of UNCLASSIFIED 00131986 060 1031089