Poking Atomic Nuclei With Lasers For Atomic Clocks And Energy Storage

Although most people are probably familiar with the different energy levels that the electron shells of atoms can be in and how electrons shedding excess energy as they return to a lower state emit for example photons, the protons and neutrons in atomic nuclei can also occupy an excited state. This nuclear isomer (metastable) state is a big part of radioactive decay chains, but can also be induced externally. The trick lies in hitting the right excitation wavelength and being able to detect the nuclear transition, something which researchers at the Technical University of Wien have now demonstrated for thorium-229.

The findings by [J.Tiedau] and colleagues were published in Physical Review Letters, describing the use of a vacuum-ultraviolet (VUV) laser setup to excite Th-229 into an isomer state. This isotope was chosen for its low-energy isomeric state, with the atoms embedded in a CaF2 crystal lattice. By trying out various laser wavelengths and scanning for the signature of the decay event they eventually detected the signal, which raises the possibility of using this method for applications like new generations of much more precise atomic clocks. It also provides useful insights into nuclear isomers as it pertains to tantalizing applications like high-density energy storage.

Although the difference in the amount of energy between the stable and semistable isomer state of a nucleus is minor in absolute terms, when compared to chemical and other forms of energy storage it can be significantly larger. Storing and releasing this energy has been the subject of research going back decades, with a 2008 paper by [E. P. Hartouni] at Lawrence Livermore National Laboratory on 178m2Hf in particular concluding that it was ‘highly improbable’ to become a practical form of energy, but this has not kept research on the topic from progressing.

One consideration here is that the number of nuclear isomers is massive, and their properties are quite distinct, as noted in a 2024 review paper by [Bhoomika Maheshwari] and colleague, along with the realization that we still miss a lot of fundamental understanding on the topic of these nuclear states. In a 2021 research paper by [Yuanbin Wu] and colleagues the long-term energy storage potential and controlled release of energy in a 93mMo isomer is studied, using electron beams as the trigger. Although still early days, this kind of research may be the path to many new technologies related to time-keeping, computing and energy storage.

5 thoughts on “Poking Atomic Nuclei With Lasers For Atomic Clocks And Energy Storage

    1. It’s not quite that intense! In the case of Th229, one shines light of the correct energy on it and the nuleus will get excited – but it won’t split. Instead, it will some time later send out a photon with that exact energy again.

      In theory this is also possible with other nuclei but every other known excited nuclear state has a much higher energy for which we are not capable of builiding the necessary “light” sources. (It’s more like x-ray sources that we’d need)

      Don’t get me wrong, Th229 is indeee unstable but it’s decay is (AFAIK) unaffected by the exctiation/deexcitation.

      1. Thanks, I read the links and got distracted by some other things and I honestly do not see it as a giant leap in time keeping standard, but maybe I’m missing something.

        Th-229 doped CaF2 crystals 2020.409(7) THz
        2 020 409(700 000 000)Hz
        hydrogen masar 1 233 030 706 593 514 Hz
        Rubidium standard 6 834 682 610.904 312 6 Hz
        Caesium standard 9 192 631 770 Hz

        From the above numbers I’m going to guess that it probably has the potential to be at least 63% better than a hydrogen masar at some future date.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.