Alpha-gamma decay studies of 253No and its daughter products 253Md , 249Fm

Abstract

Nuclear structure and decay of the isotope 253No and its decay products 249Fm and 253Md were investigated by means of $ \alpha$ - $ \gamma$ spectroscopy. Besides the established strong $ \gamma$ transitions from the $\ensuremath 9/2^{-}[734]$ Nilsson level in 249Fm , populated predominantly by the $ \alpha$ decay of 253No , into the ground-state (gs) rotational band, a couple of weaker $ \gamma$ lines (58.3, 129.2, 209.3 and 669.5keV) were observed and placed into the 249Fm level scheme. The transition from the $\ensuremath 7/2^{-}$ level in 249Es , populated by the $ \alpha$ decay of 253Md , into the $\ensuremath 9/2^{+}$ member of the gs rotational band, so far established for other odd-mass Es isotopes, was observed clearly. GEANT4 simulations were performed to investigate the influence of energy summing between $ \alpha$ particles and conversion electrons (CE) on the shape of the $ \alpha$ spectra at different implantation energies, leading to evidence for a weak $ \alpha$ decay branch of 253No into the gs of 249Fm or the ground-state rotational band, respectively.