Isobaric-multiplet mass equation in a macroscopic-microscopic approach

TL;DR

This paper evaluates the macroscopic-microscopic approach to the isobaric-multiplet mass equation, analyzing its ability to predict IMME coefficients and nuclear masses, with implications for astrophysical rp-process simulations.

Contribution

It demonstrates the effectiveness of the macroscopic-microscopic approach in describing IMME coefficients and predicts masses of proton-rich nuclei up to A=100.

Findings

Macroscopic part of FRLDM describes general trend of a and b coefficients.

Staggering behavior of b coefficients explained by proton-neutron pairing energy differences.

Predicted proton drip line aligns with experimental data.

Abstract

We study the a, b and c coefficients of the isobaric-multiplet mass equation using a macroscopic-microscopic approach developed by P. Moeller and his collaborators in ADNDT 59, 185 (1995) and ADNDT 109-110, 1 (2016). We show that already the macroscopic part of the finite-range liquid-drop model (FRLDM) describes the general trend of the a and b coefficients relatively well, while the staggering behavior of b coefficients for doublets and quartets can be understood in terms of the difference of average proton and neutron pairing energies. The sets of isobaric masses, predicted by the full macroscopic-microscopic approaches, are used to explore the general trends of IMME coefficients up to A=100. We conclude that while the agreement for a coefficients is quite satisfactory, the global approaches have less sensitivity to predict the staggering pattern observed for b coefficients of doublets and quartets. The best set of theoretical b coefficients for multiplets up to about A=100 is used to predict masses of proton-rich nuclei based on the known experimental masses of neutron-rich mirror partners, and subsequently to investigate their one- and two-proton separation energies. The estimated position of the proton-drip line is in fair agreement with known experimental data. These masses are important for simulations of the astrophysical rp-process.