High-precision mass measurement of $^{103}$Sn restores smoothness of the mass surface

TL;DR

This study achieved a high-precision direct mass measurement of $^{103}$Sn, confirming the smoothness of the nuclear mass surface and improving the accuracy of related isotopic masses, advancing understanding of doubly-magic nuclei.

Contribution

The paper presents the first high-precision direct mass measurement of $^{103}$Sn using ToF-ICR, resolving previous discrepancies and refining nuclear mass surface data.

Findings

Mass of $^{103}$Sn measured with 3.7 keV uncertainty

Confirmed agreement with recent direct measurements

Reestablished smoothness of the nuclear mass surface for $^{103}$Sn

Abstract

As a step towards the ultimate goal of a high-precision mass measurement of doubly-magic $^{100}$Sn, the mass of $^{103}$Sn was measured at the Low Energy Beam and Ion Trap (LEBIT) located at the Facility for Rare Isotope Beams (FRIB). Utilizing the time-of-flight ion cyclotron resonance (ToF-ICR) technique, a mass uncertainty of 3.7~keV was achieved, an improvement by more than an order of magnitude compared to a recent measurement performed in 2023 at the Cooler Storage Ring (CSRe) in Lanzhou. Although the LEBIT and CSRe mass measurements of $^{103}$Sn are in agreement, they diverge from the experimental mass value reported in the 2016 version of the Atomic Mass Evaluation (AME2016), which was derived from the measured $Q_{\beta^+}$ value and the mass of $^{103}$In. In AME2020, this indirectly measured $^{103}$Sn mass was classified as a `seriously irregular mass' and replaced with an extrapolated value, which aligns with the most recent measured values from CSRe and LEBIT. As such, the smoothness of the mass surface is confidently reestablished for $^{103}$Sn. Furthermore, LEBIT's mass measurement of $^{103}$Sn enabled a significant reduction in the mass uncertainties of five parent isotopes which are now dominated by uncertainties in their respective $Q$-values.