New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces

TL;DR

This paper reports high-precision mass measurements of neutron-rich calcium and potassium isotopes near N=32, revealing increased binding energies that support the importance of three-nucleon forces in nuclear structure.

Contribution

First measurement of the mass of $^{51}$K and significant improvements in calcium isotope masses, providing experimental evidence for three-nucleon force effects in neutron-rich nuclei.

Findings

$^{52}$Ca is more bound by 1.74 MeV than previous data.

Mass behavior with neutron number aligns with calculations including 3N forces.

New data supports the role of three-nucleon forces in nuclear binding energy evolution.

Abstract

We present precision Penning-trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system the mass of $^{51}$K was measured for the first time, and the precision of the $^{51,52}$Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, $^{52}$Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces at neutron-rich extremes.