Radioactive decay of Lu 178

Abstract

The decay of Lu 178 is studied after bombarding Ta with 14 MeV neutrons, separating the Lu fraction by means of radiochemistry and using standard scintillation counter techniques. A quick method for radiochemical separation of Lu, has been worked out. The beta and gamma measurements show four gamma rays of energies 90, 215, 325 and 430 keV, each decaying with half lives of 30±1 min and 5±1 min and three beta groups of maximum energies 2.25±0.05 MeV (88%), 0.770±0.06 MeV (12%) and 1.50±0.05 MeV (98%); the first two groups decaying with a half life of 5±1 min and the last one with a half life of 30±1 min. A metastable state of Lu 178m decaying with a half life of 30±1 min is suggested; the ground state Lu 178 is found to decay with a half life of 5±1 min. A conversion electron peak of 340 keV energy and a 60 keV gamma ray, later identified as the K X-ray of Lu 178m are found to decay with a half life of 30±1 min only. Coincidence studies show that the above gamma rays are in cascade and that none of the three beta groups is in coincidence with any of those above four gamma rays. Only the 0.770 MeV beta group is found to be in coincidence with the 332 keV gamma rays. A decay scheme based on the above observations is proposed and the results are discussed in the light of the unified model.