Physicists led by Prof. Thorsten Schumm from TU Wien (Vienna) have successfully excited the “thorium transition” with lasers for the first time. This breakthrough could lead to revolutionary high precision technologies, including nuclear clocks that could measure time more precisely than current atomic clocks. The team developed special thorium-containing crystals to achieve this. The discovery could also help answer fundamental questions in physics, such as whether the constants of nature change over time. The research was published in the journal “Physical Review Letters”.
The Thorium Transition: A Quantum Leap in Precision Technologies
Physicists worldwide have been on a quest for a specific state of thorium atomic nuclei, a pursuit that has spanned several decades. This state, often referred to as the “thorium transition,” holds the potential for groundbreaking advancements in precision technologies, including the development of nuclear clocks that could surpass the accuracy of the best atomic clocks currently available.
The thorium transition could also pave the way for answering fundamental questions in physics, such as whether the constants of nature are truly constant or if they fluctuate over time and space. After years of research, scientists have finally achieved this elusive thorium transition, marking a significant milestone in the field of physics.
Laser Excitation of Thorium Nucleus: A First in Physics
The thorium transition was achieved by using a laser to excite an atomic nucleus into a higher energy state and then precisely tracking its return to its original state. This process effectively bridges two areas of physics that previously had little overlap: classical quantum physics and nuclear physics.
The success of this experiment hinged on the development of special thorium-containing crystals. A research team led by Prof. Thorsten Schumm from TU Wien (Vienna), in collaboration with a team from the National Metrology Institute Braunschweig (PTB), has published their findings in the journal “Physical Review Letters.”
Overcoming the Energy Barrier: The Role of Lasers
While manipulating atoms or molecules with lasers is a common practice today, applying these techniques to atomic nuclei has long been considered impossible. This is because changing an atomic nucleus from one state to another typically requires at least a thousand times the energy of electrons in an atom or a molecule.
However, atomic nuclei are ideal quantum objects for precision measurements due to their small size and resistance to external disturbances, such as electromagnetic fields. The challenge was to find a way to manipulate atomic nuclei with lasers, a feat that was achieved with the thorium transition.
The Thorium Crystal: A Key to Unlocking the Transition
The research team developed crystals containing large numbers of thorium atoms. This approach, while technically complex, allowed the team to study not just individual thorium nuclei but also a large number of thorium nuclei simultaneously.
On November 21, 2023, the team successfully hit the correct energy of the thorium transition, and the thorium nuclei delivered a clear signal for the first time. This marked the first instance of a laser successfully changing the state of an atomic nucleus.
The Future of Precision Measurements: The Nuclear Clock and Beyond
With the successful excitation of the thorium state, this technology can now be used for precision measurements. One of the long-term goals of this research is to build a nuclear clock that would be significantly more accurate than the best atomic clocks available today.
In addition to time measurement, this technology could also be used to analyze the Earth’s gravitational field with unprecedented precision, potentially providing insights into mineral resources or earthquakes. Furthermore, it could help unravel fundamental mysteries of physics, such as the constancy of nature’s constants. As Prof. Thorsten Schumm puts it, “Our measuring method is just the beginning. We cannot yet predict what results we will achieve with it. It will certainly be very exciting.”
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