Abstract
We present a measurement of the low-energy (0–60 keV) -ray spectrum produced in the decay of using a dedicated cryogenic magnetic microcalorimeter. The energy resolution of , together with exceptional gain linearity, allows us to determine the energy of the low-lying isomeric state in using four complementary evaluation schemes. The most precise scheme determines the isomer energy to be 8.10(17) eV, corresponding to 153.1(32) nm, superseding in precision previous values based on spectroscopy, and agreeing with a recent measurement based on internal conversion electrons. We also measure branching ratios of the relevant excited states to be and .
- Received 28 May 2020
- Revised 8 July 2020
- Accepted 20 August 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.142503
© 2020 American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
Ticking Toward a Nuclear Clock
Published 28 September 2020
The high-precision measurement of a nuclear transition of a thorium isotope is a key step towards the development of a nuclear optical clock.
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