Atomic nucleus excited with laser: A breakthrough after decades

For the first time, it has been possible to use a laser to transfer an atomic nucleus into a state of higher energy and then precisely track its return to its original state. For a long time it seemed impossible to apply these techniques to atomic nuclei. "Atomic nuclei can also switch between different quantum states. However, it usually takes much more energy to change an atomic nucleus from one state to another - at least a thousand times the energy of electrons in an atom or a molecule," says Thorsten Schumm. Since the 1970s, there has been speculation that there might be a special atomic nucleus which, unlike other nuclei, could perhaps be manipulated with a laser, namely thorium-229. This nucleus has two very closely adjacent energy states - so closely adjacent that a laser should in principle be sufficient to change the state of the atomic nucleus. "Of course we are delighted that we are now the ones who can present the crucial breakthrough: The first targeted laser excitation of an atomic nucleus," says Schumm. "Similar to how a pendulum clock uses the swinging of the pendulum as a timer, the oscillation of the light that excites the thorium transition could be used as a timer for a new type of clock that would be significantly more accurate than the best atomic clocks available today."