PHYSICS / METROLOGY

LR-THORIUM-229-NUCLEAR-CLOCK-FREQUENCYOPEN LIMIT

First direct optical-frequency measurement of a nuclear clock transition

Name: First direct optical-frequency measurement of a nuclear clock transition
Creator: Limits Registry
Published: 2024-09-04T00:00:00.000Z
Keywords: PHYSICS / METROLOGY

Jun Ye's group at JILA, with TU Wien collaborators, used a vacuum-ultraviolet frequency comb to drive the thorium-229 nuclear transition in a calcium fluoride crystal and measured its frequency as 2,020,407,384,335 kHz with a 2 kHz uncertainty. Published in Nature in September 2024, it was about a million times more precise than earlier wavelength-based determinations and linked a nuclear transition to the strontium optical clock for the first time.

— page viewsSpecification version 1Published 2024-09-041 evidence records

About this problem

The question, scope, and sources behind this Registry record.

Description

Formal question

The absolute frequency of the 229Th nuclear isomeric transition, the first nuclear transition measured directly against an optical atomic clock.

Scope & constraints

Current published specification applies.

Primary sources

Zhang et al., 'Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock', Nature 633, 63 — First direct optical-frequency measurement of a nuclear clock transition JILA, Boulder, Colorado, USA

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Scope matches the published specificationNo parameters changed

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Best demonstrated value2020407384335

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Claims

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2026

CLM-THORIUM-229-NUCLEAR-CLOCK-FREQUENCY= 2020407384335CONSTRUCTIONSeventh-harmonic VUV frequency comb generated in a femtosecond enhancement cavity, phase-locked to JILA's 87Sr lattice clock, resolving individual nuclear quadrupole-split lines in 229Th:CaF2.Evidence quality: PAPER · Source: Zhang et al., 'Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock', Nature 633, 63 — First direct optical-frequency measurement of a nuclear clock transition ↗

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First direct optical-frequency measurement of a nuclear clock transition

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First direct optical-frequency measurement of a nuclear clock transition

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