α-γ and α-electron coincidence spectroscopy for a short-lived heavy actinide nucleus No257 (T1/2=24.5s) has been performed using a gas-jet transport system and an on-line isotope separator. Spin-parities of excited states in Fm253 fed by the α decay of No257 have been identified on the basis of the measured internal conversion coefficients. The ν3/2+ configuration has been assigned to the ground state of No257 as well as to the 124.1 keV level in Fm253. It was found that the ground-state configuration of No257 is different from that of lighter N=155 isotones.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)