Study of positron emission from ³⁶Cl

The absolute intensity of the weak branch for positron emission from ³⁶Cl was evaluated using a β-γ coincidence technique. A liquid sample with known activity of ³⁶Cl was embedded in scintillation cocktail and measured in a 4παβ(LS)-γ(HPGe) system that comprises a Liquid Scintillator (LS) detector and a High-Purity Germanium (HPGe) detector. The LS detector includes a photo-reflector assembly that holds the liquid sample and ensures high efficiency for β particles. The recorded timestamp and energy for β and γ events provided a highly effective mechanism for filtering out events that originated from outside the volume of the measured sample, thereby allowing a clear observation of the 511-keV γ-rays associated with positron emission from ³⁶Cl. Hence, the positron branch intensity can be evaluated directly in a practically background-free environment. The system was calibrated for detecting β particles and γ rays at relevant energies using radioactive sources having identical geometry as employed in the ³⁶Cl sample measurement. The absolute intensity of the positron emission was found to be (1.62 ± 0.15) × 10⁻⁵, in agreement with the values appearing in the literature.