STANDARDIZATION AND DECAY DATA OF GE-68/GA-68

A gamma and an x-ray spectrometer, 4 pi beta-gamma-coincidence equipment, liquid-scintillation counting (LSC) equipment and a calibrated ionization chamber (IC) have been used to determine the decay scheme parameters of Ga-68 and the specific activity of a Ge-68/Ga-68 solution. The transition probability of the positron branch and the EC branch to the ground state of Zn-68, b(1) and e(1), the corresponding branches to the 1077 keV level of Zn-68, b(2) and e(2), the total emission probability of annihilation radiation from the Ga-68 decay, p(ann), and the gamma-ray emission probabilities of the quanta corresponding to the 1077 keV transition (p(1077)) and to some weak transitions were redetermined. The results are b(1) = 0.8785 +/- 0.0012, e(1) = 0.0892 +/- 0.0012, b(2) = 0.0129 +/- 0.004, e(2) = 0.0193 +/- 0.0004, p(ann) = 1.7829 +/- 0.0022, p(1077) = 0.0322 +/- 0.0003. The specific activity of a Ge-68/Ga-68 solution was determined with a relative uncertainty of 1% (1 sigma) using 4 pi beta-gamma coincidence, LSC and IC measurements. A half-life of T-1/2 = (270.99 +/- 0.19) d for Ge-68 was obtained by measurements with an ionization chamber.