Mass measurements of 99-101In challenge ab initio nuclear theory of the nuclide 100Sn

TL;DR

This paper reports the first direct mass measurements of 99In and 101In, providing critical data to test ab initio nuclear theories of 100Sn and revealing discrepancies in its mass values.

Contribution

It presents the first direct measurements of 99In and 101In masses, challenging existing theoretical models of 100Sn's nuclear structure.

Findings

Measured 99In mass with 100-fold improved precision.

Resolved ground and isomeric states in 101In.

Identified discrepancies in 100Sn mass values from beta-decay data.

Abstract

100Sn is of singular interest for nuclear structure. Its closed-shell proton and neutron configuration exhibit exceptional binding and 100Sn is the heaviest nucleus comprising protons and neutrons in equal number, a feature that enhances the contribution of the short-range, proton-neutron pairing interaction and strongly influences its decay via the weak interaction. Decays studies in the region of 100Sn have attempted to prove its doubly magic character but few have studied it from the ab initio theoretical perspective and none have addressed the odd-proton nuclear forces. Here we present, the first direct measurement of the exotic odd-proton nuclide 100In - the beta-decay daughter of 100Sn - and 99In, only one proton below 100Sn. The most advanced mass spectrometry techniques were used to measure 99In, produced at a rate of only a few ions per second, and to resolve the ground and isomeric states in 101In. The experimental results are confronted with new ab initio many-body approaches. The 100-fold improvement in precision of the 100In mass value exarcebates a striking discrepancy in the atomic mass values of 100Sn deduced from recent beta-decay results.