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 \(α \)‑decay energies. This prompted a new experiment at the Fragment Mass Analyzer (FMA) at Argonne National Laboratory. Using the reaction \(²⁰⁹Bi(⁴⁰Ar,xn)²⁴⁹⁻ˣMd\), we performed simultaneous \(A/q\) identification and \(α \)-decay energy measurement for neutron-deficient Md isotopes. Correlated recoil-\(α \)-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