Context:
Scientists have achieved a major breakthrough in next-generation timekeeping by successfully exciting Thorium-229 nuclei in a solid-state system and detecting the emitted electrons. This development advances the concept of a nuclear clock, which could surpass atomic clocks in stability, with an accuracy so high that it would lose only one second in 15.8 billion years.
Key Highlights:
Breakthrough Experiment & Detection Method:
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Researchers detected excitation of Thorium-229 nuclei in a solid nuclear clock using a laser-based approach.
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The experiment used Thorium dioxide as the solid host material.
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Instead of detecting photons, scientists counted electrons emitted during nuclear decay.
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A clear resonance was measured at 2,020,407.5 GHz, consistent with earlier Thorium-229 studies.
Unprecedented Accuracy of Nuclear Timekeeping:
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The inferred internal conversion lifetime was 12.3 seconds.
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This corresponds to a clock accuracy of:
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Only 1 second deviation in 15.8 billion years
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Such precision exceeds current atomic clock capabilities.
Why Thorium-229 is Special:
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Thorium-229 has a unique low-energy nuclear excited state suitable for laser excitation.
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Unlike atomic clocks (based on electron transitions), nuclear clocks rely on nuclear transitions, which are:
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Less affected by external electromagnetic disturbances
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More stable across different environments
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Scientific Principle – Internal Conversion:
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Excited Thorium nuclei decay via internal conversion, where:
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Energy is transferred to an orbital electron
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The electron is emitted instead of a photon
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Researchers used timed electric fields to suppress ordinary photoelectrons and isolate delayed nuclear-decay electrons.
Applications and Future Potential:
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Enables development of:
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Ultra-stable nuclear clocks
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High-precision sensors probing nuclear environments
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Solid-state design supports miniaturisation, since the clock can be monitored by measuring emitted electron current.
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Could improve:
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Navigation systems
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Fundamental physics experiments
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Tests of variation in physical constants
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Relevant Prelims Points:
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Thorium-229: Isotope with a rare nuclear excited state enabling nuclear clocks.
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Vacuum-Ultraviolet (VUV) Lasers: Used to excite thorium nuclei.
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Internal Conversion: Nuclear decay process emitting electrons instead of photons.
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Resonance Frequency: 2,020,407.5 GHz.
Relevant Mains Points:
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Atomic vs Nuclear Clocks:
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Atomic clocks depend on electron transitions
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Nuclear clocks depend on nuclear transitions, offering greater stability
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Keywords:
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Precision Timekeeping, Quantum Sensors, Fundamental Physics, Miniaturised Clocks
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Way Forward:
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Scaling solid-state nuclear clocks for real-world deployment
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Integration into navigation and deep-space missions
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Expanding research into nuclear-based quantum technologies
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UPSC Relevance (GS-wise):
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GS 3: Advanced technology, quantum applications, scientific innovation
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Prelims: Thorium-229, internal conversion, VUV spectrum