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Probing the quantum phase transition around $N\approx60$ via mass measurements of technetium isotopes

J. Ruotsalainen, A. Jaries, M. Stryjczyk, A. Kankainen, B. Andel, M. Araszkiewicz, O. Beliuskina, A. Bruce, S. Cannarozzo, S. Chinthakayala, S. Doshi, T. Eronen, A. Fijałkowska, L. M. Fraile, P. Garczyński, Z. Ge, D. Grigorova, G. Jaworski, A. Korgul, T. Krakowski, J. Kurpeta, S. Lalkovski, M. Llanos Expósito, I. D. Moore, L. M. Motilla, M. Mougeot, H. Penttilä, A. Raggio, W. Rattanasakuldilok, J. Saren, K. Solak

TL;DR

This work provides high-precision Penning-trap masses for neutron-rich Tc isotopes around $N\approx60$ using JYFLTRAP, with $^{104,106}$Tc measured by PI-ICR and $^{105}$Tc by ToF-ICR. The new masses differ from AME20 by up to $\sim$94 keV and yield updated $Q_\beta$ values, notably reconciling $^{105}$Tc beta-decay data. The revised masses produce a flatter $S_{2n}$ trend and a smoother $\delta_{2n}$ around $N\approx60$, arguing that Tc is not part of the island of shape coexistence near $^{100}$Zr$_{60}$. These results impact nuclear-structure interpretation and reactor-decay-heat calculations, and they underscore the importance of direct Penning-trap measurements for isotopes near stability.

Abstract

The masses of neutron-rich $^{104-106}$Tc isotopes were measured using the JYFLTRAP double Penning trap and found to deviate from the Atomic Mass Evaluation 2020 by $-79(25)$, $40(12)$ and $94(41)$ keV, respectively. In the case of $^{105,106}$Tc, the updated $Q_β$ values are in agreement with a previous JYFLTRAP measurement, disagreeing with the values from the mass evaluation. The new mass values result in a more linear trend in two-neutron separation energies indicating that technetium ($Z=43$) isotopes around $N \approx 60$ are not a part of the island of shape coexistence around $^{100}$Zr$_{60}$.

Probing the quantum phase transition around $N\approx60$ via mass measurements of technetium isotopes

TL;DR

This work provides high-precision Penning-trap masses for neutron-rich Tc isotopes around using JYFLTRAP, with Tc measured by PI-ICR and Tc by ToF-ICR. The new masses differ from AME20 by up to 94 keV and yield updated values, notably reconciling Tc beta-decay data. The revised masses produce a flatter trend and a smoother around , arguing that Tc is not part of the island of shape coexistence near Zr. These results impact nuclear-structure interpretation and reactor-decay-heat calculations, and they underscore the importance of direct Penning-trap measurements for isotopes near stability.

Abstract

The masses of neutron-rich Tc isotopes were measured using the JYFLTRAP double Penning trap and found to deviate from the Atomic Mass Evaluation 2020 by , and keV, respectively. In the case of Tc, the updated values are in agreement with a previous JYFLTRAP measurement, disagreeing with the values from the mass evaluation. The new mass values result in a more linear trend in two-neutron separation energies indicating that technetium () isotopes around are not a part of the island of shape coexistence around Zr.

Paper Structure

This paper contains 4 sections, 4 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Experimental method
  3. Results and discussion
  4. Summary and Outlook

Figures (4)

  • Figure 1: Magnetron a) and cyclotron b) motion phase projections of $^{104}$Tc$^+$ ions on a 2D-MCP using the PI-ICR technique with $t_\text{acc} = 482$ ms, together with trap center spot. The isobaric contaminant $^{104}$Mo$^+$ is also identified. A dashed circle on b) indicates the average cyclotron excitation radius. The polar angles between the reference phase, the center of the trap, and the magnetron ($\alpha_-$ on a)) and cyclotron ($\alpha_+$ on b)) phase spots are marked with an arc.
  • Figure 2: Magnetron a) and cyclotron b) motion phase projections of $^{106}$Tc$^+$ ions on a 2D-MCP using the PI-ICR technique with $t_\text{acc} = 715$ ms, together with trap center spot. A dashed circle on b) indicates the average cyclotron excitation radius. The polar angles between the reference phase, the center of the trap, and the magnetron ($\alpha_-$ on a)) and cyclotron ($\alpha_+$ on b)) phase spots are marked with an arc.
  • Figure 3: Time-of-flight resonance for $^{105}$Tc$^+$ ions with a 500-ms excitation. The black data points indicate the mean time of flight of the ions for each scanned frequency $\nu_{RF}$. The solid red line is a fit of the theoretical lineshape Kretzschmar2007 to the data.
  • Figure 4: Mass trends, (a) two-neutron separation energy $S_{2n}$ and (b) two-neutron shell-gap energy $\delta_{2n}$, in the ${N\approx60}$ region plotted for isotopic chains from Zr ($Z=40$) to Rh ($Z=45$) based on the literature values from AME20 AME2020 and this work.