Researchers have observed the emission of light during the decay of a unique thorium nucleus. This discovery suggests that this particular nucleus could potentially serve as a highly accurate timekeeping device, akin to a remarkable clock.
Scientists have revealed that a unique form of thorium contains an atomic nucleus with the potential for timekeeping purposes. In an unprecedented achievement, researchers have successfully measured a specific decay of this thorium nucleus that emits a single particle of light. The precision of this energy measurement is seven times higher than previous estimations based on different decay types. This significant advancement could ignite efforts towards the development of the first-ever nuclear clock, following the footsteps of atomic clocks used for timekeeping.
According to nuclear physicist Sandro Kraemer of KU Leuven in Belgium:
“We already have remarkable atomic clocks that operate with great precision.”
These atomic clocks rely on the behavior of electrons surrounding an atom. In contrast, a nuclear clock would be based on the nucleus of the atom itself. Some scientists speculate that nuclear clocks could potentially surpass the precision of atomic clocks, which are already invaluable tools used in a wide range of applications, including GPS satellites and experiments that examine the validity of fundamental laws of physics.
The technology of atomic clocks, which is widely used and well-established, operates by utilizing the behavior of an atom’s electrons as they transition to higher energy states. This transition is triggered by light with a specific frequency, containing the precise amount of energy required for the jump. The oscillation of this light serves as the basis for the ticking mechanism of the clock. In a similar manner, a nuclear clock would rely on energy transitions within the nucleus of an atom.
The majority of atomic nuclei have energy levels that are too widely spaced to be triggered by a laser, which is essential for constructing a clock. However, a specific isotope of thorium known as thorium-229 possesses two energy levels that are remarkably close to each other, with a gap of approximately 8 electron volts. Despite this, scientists have been unable to initiate the energy jump using a laser due to the lack of precise knowledge regarding the exact size of this energy gap.
Kraemer and his colleagues conducted a measurement to determine the energy released during the decay of thorium-229 nuclei as they transitioned from a higher energy state to a lower one. To initiate the high-energy state, also known as an isomer, the team employed a method involving the use of another element that could decay into the thorium isomer. Utilizing a radioactive beam at CERN’s ISOLDE facility in Geneva, the researchers implanted actinium-229 into crystals composed of calcium fluoride and magnesium fluoride. Through the decay of actinium-229, the thorium-229 isomer was generated.
This technique proved advantageous in overcoming a challenge. Typically, the decay of thorium-229 involves transferring its energy to an electron, causing it to be ejected from the atom, making the energy measurement challenging. However, the decay that releases a photon, or a particle of light, is much more easily measurable. Nonetheless, this type of decay occurs only once in a billion decays under normal circumstances.
According to quantum physicist Simon Stellmer from the University of Bonn in Germany, who was not part of the research team, this achievement is a significant milestone that scientists have been eagerly anticipating. Previous assertions about detecting this particular decay type have not stood up to scrutiny, but Stellmer believes that this observation represents the genuine and first true detection of this isomer decay.
Scientists are currently engaged in the task of utilizing a laser to initiate the energy transition, specifically moving from the low-energy state to the higher-energy isomer. This marks a crucial advancement in the development of a nuclear clock. Physicist Ekkehard Peik from the National Metrology Institute of Germany in Braunschweig, who was not part of the recent study, expressed enthusiasm about this progress, stating that their laboratory is actively working on achieving this milestone.
The advent of a nuclear clock opens up new possibilities for studying physics phenomena. Physicist Ekkehard Peik highlights the significance of comparing nuclear clocks with conventional atomic clocks, as they are based on different underlying physics principles. This comparison could potentially unveil subtle variations in fundamental constants of nature, offering fresh insights into the fundamental laws governing our universe.
In addition to the aforementioned advantages, the use of nuclei in solid materials for nuclear clocks offers an additional benefit. Unlike atomic clocks, which require atoms to be suspended within a vacuum chamber, nuclear clocks can utilize nuclei within solid materials. This characteristic allows for enhanced stability and faster measurement capabilities. The potential for a more stable and efficient nuclear clock is a promising prospect, as highlighted by physicist Sandro Kraemer.