Towards the Limits of Stability — New Decay Study of the Lightest Mendeleviums

Recent decay studies of \(^{244,245}\)Md at the GSI Helmholtzzentrum für Schwerionenforschung, Germany, and at the Lawrence Berkeley National Laboratory (LBNL) reported conflicting mass assignments to similar \(\alpha \)‑decay energies. This prompted a new experiment at the Fragment Mass Analyzer (FMA) at Argonne National Laboratory. Using the reaction \(^{209}\mathrm {Bi}(^{40}\mathrm {Ar},xn)^{249-x}\mathrm {Md}\), we performed simultaneous \(A/q\) identification and \(\alpha \)-decay energy measurement for neutron-deficient Md isotopes. Correlated recoil-\(\alpha \)-decay chains belonging to \(^{247}\)Md and \(^{245}\)Md were identified. Probabilistic mass identification was performed from focal-plane position using a test reaction, yielding consistent \(A=247\) and \(A=245\) mass assignments within uncertainties. This study re-examines the production cross sections, decay energies, and isotopic assignments for the \(^{247}\)Md and \(^{245}\)Md nuclei. Abstract Published by the Jagiellonian University 2026 authors