Optical transition of the 229^{229}229Th nucleus in a solid-state environment (original) (raw)
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Journal of Luminescence, 2013
Optical spectroscopy of an atomic nucleus: Progress toward direct observation of the 229Th isomer transition Report Title The nucleus of the thorium-229 isotope possesses a first excited nuclear state (229mTh) at an exceptionally low energy of 7.8±0.5 eV above the nuclear ground state (229gTh), as determined by earlier indirect measurements. This is the only nuclear excited state known that is within the range of optical spectroscopy. This paper reports progress toward detecting the 229mTh state directly by luminescence spectroscopy in the vacuum ultraviolet spectral region. The estimated natural linewidth of the 229gTh?229mTh isomer transition of 2?×0.1 to 2?×10 mHz is expected to broaden to ?10 kHz for 229Th4+ doped into a suitable crystal. The factors governing the choice of crystal system and the substantial challenges in acquiring a sufficiently large quantity of 229Th are discussed. We show that the 229gTh?229mTh transition energy can be identified to within 0.1 nm by luminescence excitation and luminescence spectroscopy using the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. This would open the door for subsequent laser-based measurements of the isomer transition and future applications of 229Th in nuclear clocks. We also show that 233U-doped materials should produce an intrinsic, continuous, and sufficiently high rate of 229mTh?229gTh luminescence and could be a useful aid in the initial direct search of the isomer transition. Optical spectroscopy of an atomic nucleus: Prog Approved for public release; distribution is unlimited.
Physical Review Letters, 2010
We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229 Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229 Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solid-state optical frequency reference that surpasses the short-term stability of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision (short-term stability) of 3 Â 10 À17 < Áf=f < 1 Â 10 À15 after 1 s of photon collection may be achieved with a systematic-limited accuracy (long-term stability) of Áf=f $ 2 Â 10 À16. Improvement by 10 2 À 10 3 of the constraints on the variability of several important fundamental constants also appears possible.
Direct Search for Low Energy Nuclear Isomeric Transition of Th-229m With TES Detector
IEEE Transactions on Applied Superconductivity, 2021
Precise knowledge of the energy and lifetime of 229m Th isomeric state has notable importance as a basis for a nuclear clock. Such a clock would be capable to extend precision on the oscillator frequency by up to four orders of magnitude compared to the presently best atomic clocks. However, the technique proposed for the clock requires that the isomeric state energy is accessible with existing laser systems. Previous measurement placed this state at ∼8 eV (150 nm), in the Vacuum Ultra Violet (VUV) range of the electromagnetic spectrum. A precise direct measurement of the energy of this state is necessary to determine whether the nuclear clock can be made using existing laser technology. We are developing a cryogenic microcalorimeter to measure the energy and lifetime of the 229m Th isomeric state directly. The experiment will use a 233 U source whose alpha-decay will populate the 229m Th isomeric state with 2% probability. The subsequent decay of 229m Th will be measured by a Transition Edge Sensor (TES) with <1 eV resolution. Such a technique will allow to observe all possible types of decays of 229m Th in the range of energy from 3 to 50 eV and lifetimes >5 microseconds. The single-photon TES has sufficient resolving power combined with high efficiency in the whole energy band for this experiment. Here we present a prototype of TES based on a 200 nm thick iridium-gold (Ir/Au) film which was tested with a pulsed laser source and demonstrated ∼0.8 eV energy resolution and 5.8 ± 2.1 µs signal recovery time.
Atomic clock with a nuclear transition: solid state approach at TU Wien
The nucleus of 229 Thorium presents a unique isomer state of very low energy and long lifetime, current estimates are around 7.8 eV and seconds to hours respectively. This nuclear transitions therefore is a promising candidate for a novel type of frequency standard and severly groups worldwide have set out to investigate this system. Our aim is to construct a "solid state nuclear clock", i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride crystals transparent in vacuum ultraviolet range. As a first step towards an accurate determination of the exact energy and lifetime of this isomer state we perform low-resolution fluorescent spectroscopic measurements.
Atomic clock with nuclear transition: current status in TU Wien
The nucleus of 229 Thorium presents a unique isomer state of very low energy and long lifetime, current estimates are around 7.8 eV and seconds to hours respectively. This nuclear transitions therefore is a promising candidate for a novel type of frequency standard and severly groups worldwide have set out to investigate this system. Our aim is to construct a "solid state nuclear clock", i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride crystals transparent in vacuum ultraviolet range. As a first step towards an accurate determination of the exact energy and lifetime of this isomer state we perform low-resolution fluorescent spectroscopic measurements.
Performance of a 229Thorium solid-state nuclear
2016
The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as a clock transition in a new type of optical frequency standard. Here we discuss the construction of a "solid-state nuclear clock" from Thorium nuclei implanted into single crystals transparent in the vacuum ultraviolet range. We investigate crystalinduced line shifts and broadening effects for the specific system of Calcium fluoride. At liquid Nitrogen temperatures, the clock performance will be limited by decoherence due to magnetic coupling of the Thorium nuclei to neighboring nuclear moments, ruling out the commonly used Rabi or Ramsey interrogation schemes. We propose clock stabilization based on a flourescence spectroscopy method and present optimized operation parameters. Taking advantage of the high number of quantum oscillators under continuous interrogation, a fractional instability level of 10 −19 might be reached within the solid-state approach.
Performance of a 229 Thorium solid-state nuclear clock
New Journal of Physics, 2012
The 7.8 eV nuclear isomer transition in 229 thorium has been suggested as a clock transition in a new type of optical frequency standard. Here we discuss the construction of a 'solid-state nuclear clock' from thorium nuclei implanted into single crystals transparent in the vacuum ultraviolet range. We investigate crystal-induced line shifts and broadening effects for the specific system of calcium fluoride. At liquid nitrogen temperatures, the clock performance will be limited by decoherence due to magnetic coupling of the thorium nuclei to neighboring nuclear moments, ruling out the commonly used Rabi or Ramsey interrogation schemes. We propose clock stabilization based on a fluorescence spectroscopy method and present optimized operation parameters. Taking advantage of the large number of quantum oscillators under continuous interrogation, a fractional instability level of 10 −19 might be reached within the solid-state approach.