Evaluating the intensity of the ‘prompt’ 140.5 keV γ-ray of 99Mo using a 4παβ(LS)-γ(HPGe) measurement system

S. Nissim, O. Aviv, M. Brandis, L. Weissman, R. Sasson, Z. Yungrais, H. Datz, L. Arazi

Research output: Contribution to journalArticlepeer-review


The absolute intensity for the ‘prompt’ 140.5 keV gamma-ray of 99Mo was evaluated using the β-γ coincidence technique. A liquid sample of 99Mo was prepared from a99Mo/99mTc generator and measured in a 4παβ(LS)-γ(HPGe) system that comprises a Liquid Scintillator (LS) detector and a High-Purity Germanium (HPGe) detector. The sample was introduced into scintillation fluid embedded in a photo-reflector assembly that provides almost 100% efficiency for detecting β particles (in the energy range of intreset). The combination of the HPGe and the LS detectors provided a highly effective rejection mechanism for non-coincident events. Thereby, the distinction between the detected 140.5 keV events originating from decays of 99mTc (IT) and those from transitions bypassing the metastable state could be obtained and the ‘prompt’ intensity was evaluated directly. The system was calibrated for detecting β particles and γ-rays using radioactive sources of known activities and having identical geometry as the sample containing 99Mo. The absolute intensity of the ‘prompt’ 140.5 keV was found to be (5.21 ± 0.02stat±0.16sys)%, in good agreement with results from more recently reported works.

Original languageAmerican English
Article number110367
JournalApplied Radiation and Isotopes
StatePublished - 1 Oct 2022


  • Gamma-ray intensity
  • Gamma-ray spectrometry
  • HPGe detector
  • LSC
  • Mo/Tc

All Science Journal Classification (ASJC) codes

  • Radiation


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