Solving the 244,245Md puzzle

by Shayan Kumar, 2^d year PhD student at GANIL

The investigation of neutron-deficient and neutron-rich isotopes of heavier nuclei offers profound insights into the nuclear structure and the limits of stability for extreme numbers of protons and neutrons beyond the beta-stability line, especially in the region of shell closures and sub-shell closures (around Z=100). To uncover the stability limits and also the effect of the single-particle states on the decay modes, the neutron-deficient mendelevium, ^244,245Md (Z=101) isotopes were the subject of study in two recent experiments at GSI and Berkley. The results of the two experiments raised a debate on the mass assignment of these observed isotopes of mendelevium(Md).
The α-decay energies of the reported ²⁴⁴Md in the experiment at Berkley were assigned to the neighboring isotope ²⁴⁵Md in a contemporaneous and also in an earlier experiment at GSI. To clarify the mass assignment by the Berkley group performed in a two-step (mass assignment and decay spectroscopy of ²⁴⁴Md) procedure, a new experiment will be conducted next month at the fragment mass analyzer (FMA) of Argonne National Laboratory (ANL) ATLAS facility measuring α-decay energies and atomic mass of the evaporation residues at the same time.
In this contribution, I will discuss the conflict in opinion regarding the discovery of the most neutron-deficient isotope of Md and the proposed new experiment at ANL to solve this disagreement.