Alpha-gamma decay studies of 261Sg and 257Rf

The isotope 261Sg and its decay product 257Rf were produced in the nuclear reaction 208Pb(54Cr, n)261Sg . The radioactive decay of these isotopes was investigated by means of $ \alpha$ , $ \alpha$ - $ \gamma$ and/or $ \alpha$ -X-ray spectroscopy. Improved spectroscopic data concerning $ \alpha$ energies, $ \gamma$ transitions, tentative spin and parity assignments of low-lying Nilsson single-neutron orbitals are presented for these nuclei.