Direct determination of the excitation energy of quasi-stable isomer $^{180m}$Ta

TL;DR

This paper reports the first direct measurement of the excitation energy of the quasi-stable isomer $^{180m}$Ta using Penning-trap mass spectrometry, achieving higher accuracy than previous evaluations and aiding research in dark matter, gamma lasers, and astrophysics.

Contribution

The study provides the first direct measurement of $^{180m}$Ta's excitation energy, improving accuracy over previous indirect estimates.

Findings

Excitation energy of $^{180m}$Ta is 76.79(55) keV.

First direct measurement of this isomer's excitation energy.

Enhanced precision over previous evaluation values.

Abstract

$^{180m}$Ta is a naturally abundant quasi-stable nuclide and the longest-lived nuclear isomer known to date. It is of interest for, among others, the search for dark matter, for the development of a gamma laser and for astrophysics. So far, its excitation energy has not been measured directly but has been based on an evaluation of available nuclear reaction data. We have determined the excitation energy of this isomer with high accuracy using the Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between the ground and isomeric states of $^{180}$Ta yields an excitation energy of 76.79(55) keV for $^{180m}$Ta. This is the first direct measurement of the excitation energy and provides a better accuracy than the previous evaluation value, 75.3(14) keV.