Towards complete decay spectroscopy of 152Tb

The radionuclide 152 Tb, decaying by β + emission and electron capture to 152 Gd with T 1 / 2 = 17.8784(95) h, has been shown in its first-in-human use to be suitable for positron emission tomography (PET) imaging. As a member of the terbium theragnostic quartet, this radionuclide has potential applications in personalised cancer treatments. Sources of 152 Tb were produced by proton-induced spallation of a tantalum target followed by on-line mass separation at CERN-ISOLDE. The sources were delivered to ILL Grenoble, where gamma-gamma coincidence spectroscopy of excited states populated in 152 Gd following the decay was carried out using the Fission Product Prompt γ -ray Spectrometer (FIPPS). Preliminary analysis has resulted in the identification of multiple previously unreported excited states in 152 Gd, thirteen of which are reported here at excitation energies up to 3746 keV. Angular correlation analysis has been used to provide initial spin and parity assignments to excited states. The result of the completed spectroscopy will be a revised gamma-ray and β + dose to patients compared to the current expected values. • Thirteen previously unreported excited states identified following the decay. • New placements for fourteen gamma-ray transitions proposed. • Excited state spin and parity assigned. • Ongoing analysis expected to further extend the level scheme of this decay. • Updated level scheme will lead to revised radiation dose to cancer patients.