Decay of 89Sr and the emission probability of the 909.12 keV gamma-ray transition

Gamma-ray emission rates have been measured for highly pure sources of 89Sr. These sources were prepared with relative 85Sr activity ratios that ranged from less than 0.006% to undetectable, and had been previously standardized for radioactive concentration. Three such source materials were measured using Ge spectrometers, and the probability per decay of the 909.12 keV gamma ray was found to be 9.555×10−5 with a relative expanded uncertainty of 1.26%. This result and other reported probabilities per decay have been evaluated according to the protocol of the International Atomic Energy Agency Coordinated Research Program on the Measurement and Evaluation of X-ray and Gamma-ray Standards for Detector Efficiency Calibration. This evaluation yielded a recommended value of 9.559×10−5 with a relative standard uncertainty 0.47% for the probability per decay of the 909.12 keV gamma ray.