Physicists used a benchtop laser to put an atomic nucleus into a higher energy state. This achievement marks a new stage in creating the first nuclear clock that would tell time based on the internal workings of atomic nuclei. Olga Kocharovskaya, a physicist at Texas A&M University in College Station, says this is a new scientific breakthrough.
Atomic and nuclear clocks: what is the difference?
Atomic clocks are currently the most accurate chronometers available to scientists, but a nuclear clock could be simpler and more portable compared to them. It could be used to test fundamental physical theories in new ways.
Atomic clocks are based on the physics of electrons surrounding atoms. Inside atoms, electrons are at separate energy levels. For an electron to move to another energy level, a certain amount of energy from a laser must be directed at it. This energy has its own frequency, and to determine it, scientists direct a laser at a set of atoms. When the electron moves to another level, they record the frequency of the laser, which is the atomic metronome for keeping time.
In turn, a nuclear clock uses the transition to other levels of atomic nuclei, not electrons, to measure time. However, most atomic nuclei have energy levels that are too far apart for a laser to affect them. The exception is the thorium element nucleus, thorium-229.
The result of the experiment
The researchers used a laser to push the thorium-229 nuclei to a higher energy level and observed the light emitted. The experiment made it possible to determine the transition energy: it is 8.35574 electrons/volts.
This number is consistent with measurements made in 2023 but is about 800 times more accurate. To create a nuclear clock, scientists will need to improve the accuracy of such measurements, but the first step in this direction has already been taken.