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

The absolute intensity for the 'prompt' 140.5 keV gamma-ray of Mo was evaluated using the β-γ coincidence technique. A liquid sample of Mo was prepared from aMo/Tc 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 Tc (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 Mo. The absolute intensity of the 'prompt' 140.5 keV was found to be (5.21 ± 0.02±0.16)%, in good agreement with results from more recently reported works.