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Accessible Nuclear Transiºon in Thorium-‐229

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Accessible Nuclear Transiºon in Thorium-‐229 New results on the laser-accessible nuclear transion in Thorium-229 Thorsten Schumm Ins2tute for Atomic and Subatomic Physics University of Technology, Vienna www.quantummetrology.at New results on 229Th Outline Introduction: nuclear physics with a laser? • The low-energy nuclear transition in 229Thorium • On nuclear clocks and fundamental constants Thorsten Schumm New results on Th-229 1 out of 44 New results on 229Th Outline Introduction: nuclear physics with a laser? • The low-energy nuclear transition in 229Thorium • On nuclear clocks and fundamental constants Experiment 1: Gamma measurements • A brief history of the 229Th isomer energy • The 2007 Beck et al. gamma measurement • The 2020 measurement: isomer energy + branching ratio Experiment 2: IC measurements • The 2017 LMU measurement: proof of existence • The 2018 PTB + LMU measurement: optical transitions • The 2019 measurement: isomer energy Experiment 3: X-ray pumping • The 2019 SPring-8 experiment: isomer pumping + isomer energy + branching ratio Thorsten Schumm New results on Th-229 1 out of 44 New (?) results on 229Th Outline Introduction: nuclear physics with a laser? • The low-energy nuclear transition in 229Thorium • On nuclear clocks and fundamental constants Experiment 1: Gamma measurements • A brief history of the 229Th isomer energy • The 2007 Beck et al. gamma measurement • The 2020 measurement: isomer energy + branching ratio Experiment 2: IC measurements • The 2017 LMU measurement: proof of existence • The 2018 PTB + LMU measurement: optical transitions • The 2019 measurement: isomer energy Experiment 3: X-ray pumping • The 2019 SPring-8 experiment: isomer pumping + isomer energy + branching ratio Thorsten Schumm New results on Th-229 1 out of 44 New results on 229Th Questions ??? Please ask anytime! Thorsten Schumm New results on Th-229 2 out of 44 New results on 229Th Outline Introduction: nuclear physics with a laser? • The low-energy nuclear transition in 229Thorium • On nuclear clocks and fundamental constants Experiment 1: Gamma measurements • A brief history of the 229Th isomer energy • The 2007 Beck et al. gamma measurement • The 2020 measurement: isomer energy + branching ratio Experiment 2: IC measurements • The 2017 LMU measurement: proof of existence • The 2018 PTB + LMU measurement: optical transitions • The 2019 measurement: isomer energy Experiment 3: X-ray pumping • The 2019 SPring-8 experiment: isomer pumping + isomer energy + branching ratio Thorsten Schumm New results on Th-229 3 out of 44 Nuclear physics with a laser? The gap between atomic and nuclear physics Atomic physics electron discrete energy levels eV excited states 1.0 nucleus ground 0 state 10-10 m main tool of study: laser spectroscopy Atomic spectroscopy for metrology • provides a frequency standard • 1s ≡ 9.192.631.770 oscillations in Cs • crucial for fundamental research • applications: GPS, communication • miniaturization possible Thorsten Schumm New results on Th-229 4 out of 44 Nuclear physics with a laser? The gap between atomic and nuclear physics Atomic physics Nuclear physics electron discrete energy levels protons discrete energy levels eV neutrons MeV excited excited states states 1.0 1.0 nucleus ground ground 0 state 0 state 10-14 m 10-10 m main tool main tool of study: of study: laser particle spectroscopy accelerators Atomic spectroscopy for metrology Nuclear spectroscopy for metrology • provides a frequency standard • no frequency standard (although suited!) • 1s ≡ 9.192.631.770 oscillations in Cs • used in fundamental research • crucial for fundamental research • (Mössbauer spectroscopy, dating) • applications: GPS, communication • no direct metrology applications • miniaturization possible • no miniaturization Thorsten Schumm New results on Th-229 4 out of 44 Nuclear physics with a laser? The gap between atomic and nuclear physics Atomic physics Nuclear physics electron discrete energy levels protons discrete energy levels eV neutrons MeV excited excited states states 1.0 1.0 nucleus ground ground 0 state 0 state 10-14 m 10-10 m main tool main tool of study: of study: laser particle spectroscopy accelerators Atomic spectroscopy for metrology Nuclear spectroscopy for metrology • provides a frequency standard • NEW frequency standards ? • 1s ≡ 9.192.631.770 oscillations in Cs • new fundamental research possible ! • crucial for fundamental research • (Mössbauer spectroscopy, dating) • applications: GPS, communication • miniaturization possible • miniaturization possible • applications ahaid? Thorsten Schumm New results on Th-229 4 out of 44 Nuclear physics with a laser? The low-energy nuclear transition in 229Th Isotopes with low-lying excited states: Tc-99 2150 eV Hg-201 1561 eV W-183 544 eV U-235 76 eV ≈ 17 nm Th-229 ~8 eV ≈ 150 nm Thorsten Schumm New results on Th-229 5 out of 44 Nuclear physics with a laser? The low-energy nuclear transition in 229Th MeV 229 229 3 + Th isomer state 90 Th [631] excited 2 states 7880a M1 transition α: 4.845 MeV 1.0 ΔE ≈ 8 eV τ ≈ min. – h. 1st excited state 0 5 + ground state [633] 2 229Th ground state Jakob Berzelius 1829 Isotopes with low-lying excited states: Tc-99 2150 eV Hg-201 1561 eV W-183 544 eV U-235 76 eV ≈ 17 nm Th-229 ~8 eV ≈ 150 nm Thorsten Schumm New results on Th-229 5 out of 44 Nuclear physics with a laser? The low-energy nuclear transition in 229Th MeV 229 229 3 + Th isomer state 90 Th [631] excited 2 states 7880a M1 transition α: 4.845 MeV 1.0 ΔE ≈ 8 eV τ ≈ min. – h. 1st excited state 0 5 + ground state [633] 2 229Th ground state Jakob Berzelius 1829 229Thorium facts : L radio isotope : half life 7880 years, very rare, totally artificial substance L ionization energies: 6.1 eV, 11.5 eV, 20 eV → need to work with the ion -21 2 L low scattering cross section (estimated σ ≈ 10 cm ) (a single Rb Atom has 10-9 cm2) L no easy (tunable) excitation source at 150 nm (VUV) Thorsten Schumm New results on Th-229 5 out of 44 Nuclear physics with a laser? The low-energy nuclear transition in 229Th MeV 229 229 3 + Th isomer state 90 Th [631] excited 2 states 7880a M1 transition α: 4.845 MeV 1.0 ΔE ≈ 8 eV τ ≈ min. – h. 1st excited state 0 5 + ground state [633] 2 229Th ground state Jakob Berzelius 1829 229Thorium facts : L radio isotope : half life 7880 years, very rare, totally artificial substance L ionization energies: 6.1 eV, 11.5 eV, 20 eV → need to work with the ion -21 2 L low scattering cross section (estimated σ ≈ 10 cm ) (a single Rb Atom has 10-9 cm2) L no easy (tunable) excitation source at 150 nm (VUV) J narrow transition for a frequency standard a solid-state J robust nuclear transition „nuclear“ J can be embedded in a crystal clock ? Thorsten Schumm New results on Th-229 5 out of 44 Nuclear physics with a laser? The low-energy nuclear transition in 229Th MeV 229 229 3 + Th isomer state 90 Th [631] excited 2 states 7880a M1 transition α: 4.845 MeV 1.0 ΔE ≈ 7.8±0.5eV τ ≈ min. – h. 1st excited state 0 5 + ground state [633] 2 229Th ground state Jakob Berzelius 1829 229Thorium facts : L radio isotope : half life 7880 years, very rare, totally artificial substance L ionization energies: 6.1 eV, 11.5 eV, 20 eV → need to work with the ion -21 2 L low scattering cross section (estimated σ ≈ 10 cm ) (a single Rb Atom has 10-9 cm2) L no easy (tunable) excitation source at 150 nm (VUV) J narrow transition for a frequency standard a solid-state „nuclear“ search for J robust nuclear transition drifts in clock ? J can be embedded in a crystal fundamental J very high sensitivity to the fine structure constant constants? Thorsten Schumm New results on Th-229 5 out of 44 Nuclear physics with a laser? Why a “nuclear clock”? – figure of merit Atom Ideal atomic clock: 1 Laser Detektor unperturbed atomic f S transition frequency νo m f0 m (at v = 0, T = 0) f0 f a k z Absorptions- Δp n Regelungs- Δν e signal probability transition u elektronik dS q e df 0 r f F f -15 -10 -5 0 5 10 15 Fehlersignal 0 νo what makes a good „clock transition“? Δν : linewidth, ideally Fourier limited ~1/Texc., requires stable atomic levels Δp : measurement noise, ideally projection noise/Fourier limited ν Quality factor of a clock transition: Q = 0 Δν Thorsten Schumm New results on Th-229 6 out of 44 Nuclear physics with a laser? Why a “nuclear clock”? – figure of merit Atom Ideal atomic clock: 1 Laser Detektor unperturbed atomic f S transition frequency νo m f0 m (at v = 0, T = 0) f0 f a k z Absorptions- Δp n Regelungs- Δν e signal probability transition u elektronik dS q e df 0 r f F f -15 -10 -5 0 5 10 15 Fehlersignal 0 νo what makes a good „clock transition“? Δν : linewidth, ideally Fourier limited ~1/Texc., requires stable atomic levels Δp : measurement noise, ideally projection noise/Fourier limited ν to build a good clock... Figure of merit*: Quality factor of a clock transition: Q = 0 • use high transition frequency Δν ν0 • use narrow transition (small Δν) • have many oscillators (large N) F = Q N Standard quantum limit: Δν ≈ 1/ NT τ int av • have long interrogation time Tint for Texc. >> Tint,τ av assuming Δν ≈ 1 / (T τ )-1/2 ideal: solid-state nuclear int av independent of N Thorsten Schumm New results on Th-229 6 out of 44 Nuclear physics with a laser? What about “fundamental constants”? isomeric state 7.8 eV + δω ground state ... binding energy/nucleon Mev binding energy 0 ⎛ X ⎞ 103-105 enhancement in sensitivity! δω 5 δα δ q δX s (exact value under vivid discussion!) ≈10 ⎜4 + −10 ⎟ ⎜ X X ⎟ 229 ω ⎝ α q s ⎠ comparing the Th nuclear transition frequency to standard atomic clocks mq m may allow to look for variations of at with X s α q = X s = -18 -20 ΛQCD ΛQCD 10 - 10 per year mq, ms light/strange quark mass (5/120 MeV) fundamental physics in a quantum chromodynamic scale ΛQCD tabletop experiment? Thorsten Schumm New results on Th-229 7 out of 44 New results on 229Th Questions ??? Maybe now? Thorsten Schumm New results on Th-229 8 out of 44 New results on 229Th Outline Introduction: nuclear physics with a laser? • The low-energy nuclear transition in 229Thorium • On nuclear clocks and fundamental constants Experiment 1: Gamma measurements • A brief history of the 229Th isomer energy • The 2007 Beck et al.
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