Scandium-based nuclear clocks promise punctuality for next 300 billion years

It's about time!

Set your watches! Scientists have set the clock ticking for the development of a new generation of timepieces with accuracy of up to 1 second in 300 billion years or about 22 times the age of the universe.

Researchers working at European XFEL X-ray have examined the potential of scandium as the basis for nuclear clocks, long seen as the next step forward in accuracy over the current generation of atomic clocks.

Most atomic clocks rely on oscillators such as caesium, which can oscillate at very reliable frequencies when excited by microwave radiation. For example, the US Department of Commerce's National Institute of Standards and Technology's NIST-F2 clock would neither gain nor lose one second in about 300 million years.

But scientists have held the ambition of going one step further by using the oscillation of the atomic nucleus – rather than the electron shell – to create the next level in timekeeping.

At the European XFEL X-ray laser, researchers have found a promising candidate in the element scandium. Readily available as a high-purity metal foil or as the compound scandium dioxide, the element's atomic resonances are much more acute than those of electrons in the atomic shell.

However, they are trickier to get wobbling, requiring X-rays with an energy of 12.4 kiloelectronvolts, about 10,000 times the energy of visible light. Such excitement produces an extremely narrow resonant width, a key factor in clock accuracy. The researchers showed a width of only 1.4 femtoelectronvolts, 1 x 10-15 eV, which might make an accuracy of 1:10,000,000,000,000 possible.

Ralf Röhlsberger, researcher at Germany's Deutsches Elektronen-Synchrotron, was part of the team. He said the level of accuracy possible from a nuclear clock using scandium could be equivalent to one second in 300 billion years, according to a statement.

In other words, if your watch loses a second a year, it will be 9,512 years slow by the time a nuclear clock based on scandium is a second out.

The research group was led by Yuri Shvyd'ko, senior physicist at the Argonne National Laboratory in Lemont, Illinois.

Releasing the news in a paper published in the journal Nature, the researchers said: "These advancements enable the application of this isomer in extreme metrology, nuclear clock technology, ultra-high-precision spectroscopy and similar applications." ®

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