Speaker
Description
The exploration of neutron-deficient isotopes in the vicinity of the Z = 100 shell gap, offers valuable insight into the nuclear structure and the boundaries of stability for nuclei with extreme neutron-to-proton ratios. To investigate the limits of stability and also the effects of the single-particle states on the decay modes of these nuclei, the neutron-deficient isotopes of mendelevium ($^{244,245}$Md) were the subject of study in two recent experiments at GSI$^{[1]}$ and Lawrence Berkeley National Laboratory (LBNL)$^{[2,3]}$. The results of the two experiments initiated a debate$^{[4]}$ on the mass assignment to the observed alpha ($\alpha$) decay chains of the mendelevium isotope.
The $\alpha$-decay energies of the reported $^{244}$Md events in the experiment at Berkeley were assigned to the neighboring isotope $^{245}$Md in a contemporaneous as well as an earlier experiment at GSI$^{[5]}$. To resolve the disparity between the results from LBNL and GSI, a new experiment was conducted in May-June, 2024 at the Fragment Mass Analyzer (FMA)$^{[6]}$ located at the Argonne Tandem Linear Accelerator System (ATLAS) facility of Argonne National Laboratory (ANL). In this experiment, instead of the two-step procedure applied at Berkeley$^{[2,3]}$, the mass (A) and $\alpha$-decay energies (E$_\alpha$) of the evaporation residues (ERs) were measured simultaneously. This was achieved using the mass-separation capability of FMA in conjunction with the focal plane decay station, consisting of silicon detectors arranged in a box configuration surrounded by five germanium clover detectors.
The aim of this experiment was to resolve the discrepancy and assign proper $\alpha$-decay energies to the mass-identified isotopes of mendelevium, and to establish a production cross-section for the isotope of mendelevium in question. The first analysis of the experimental data indicates the occurrence of events at the utilized beam energy that correspond to the reported E$_\alpha$ of $^{245}$Md $^{[1]}$. In this contribution, the results from the experimental data analysis will be presented.
References
[1] J. Khuyagbaatar et al., Phys. Rev. Lett. 125, 142504 (2020)
[2] J. L. Pore et al., Phys. Rev. Lett. 124, 252502 (2020)
[3] J. M. Gates and J. L. Pore, Eur. Phys. J. A 58, 1 (2022)
[4] F. P. Heßberger et al., Phys. Rev. Lett. 126, 182501 (2021)
[5] V. Ninov et al., Zeitschrift für Physik A Hadrons and Nuclei 356, 11 (1996)
[6] C. N. Davids et al., Nucl. Instr. and Meth. B 70 (1992)
