Highly charged ions in Penning traps, a new tool for resolving low lying isomeric states

TL;DR

This paper demonstrates that highly charged ions in Penning traps significantly enhance the resolution for detecting low-lying nuclear isomers, enabling precise measurements and opening new avenues for isomer research.

Contribution

It introduces a novel method using highly charged ions in Penning traps to resolve and measure low-lying nuclear isomers with improved precision.

Findings

Resolved the $^{78}$Rb isomeric state from the ground state.

Measured the isomer's excitation energy as 108.7 keV.

Confirmed mass measurements agree with existing nuclear data.

Abstract

The use of highly charged ions increases the precision and resolving power, in particular for short-lived species produced at on-line radio-isotope beam facilities, achievable with Penning trap mass spectrometers. This increase in resolving power provides a new and unique access to resolving low-lying long-lived ($T_{1/2} > 50$ ms) nuclear isomers. Recently, the $111.19(22)$ keV (determined from $\gamma$-ray spectroscopy) isomeric state in $^{78}$Rb has been resolved from the ground state, in a charge state of $q=8+$ with the TITAN Penning trap at the TRIUMF-ISAC facility. The excitation energy of the isomer was measured to be $108.7(6.4)$ keV above the ground state. The extracted masses for both the ground and isomeric states, and their difference, agree with the AME2003 and Nuclear Data Sheet values. This proof of principle measurement demonstrates the feasibility of using Penning trap mass spectrometers coupled to charge breeders to study nuclear isomers and opens a new route for isomer searches.