In a groundbreaking development, an international research team has propelled atomic clocks (nuclear clocks) into a new era by utilizing nuclear transitions in atomic scandium instead of electronic transitions. Conducted at the European X-Ray Free-Electron Laser facility, this advance is poised to usher in a thousandfold increase in timekeeping precision, as detailed in the journal Nature.
Atomic clocks, renowned for their accuracy, have traditionally relied on electronic transitions within the atomic shell of elements like cesium to define time. Microwaves with a known frequency elevate electrons to higher energy levels, resulting in microwave absorption—a phenomenon known as resonance. The stability of cesium atomic clocks is such that they remain accurate to within one second over an astonishing 300 million years.
NUCLEUS OF SCANDIUM
Key to this accuracy is the narrow width of the resonance used. While current cesium clocks already employ a remarkably narrow resonance, scientists worldwide have been exploring the concept of a “nuclear” clock for years. Unlike electron resonances, nuclear resonances are sharper but considerably more challenging to excite.
This recent breakthrough involves exciting a promising transition in the nucleus of scandium, an element readily available in high-purity metal foil or as scandium dioxide. The success in resonantly exciting scandium’s nucleus not only propels nuclear clocks forward but also opens avenues for ultrahigh-precision spectroscopy and measuring fundamental physical effects with unprecedented accuracy.
Yuri Shvydko of Argonne National Laboratory remarks, “The breakthrough in resonant excitation of scandium and the precise measurement of its energy opens new avenues not only for nuclear clocks but also for ultrahigh-precision spectroscopy and precision measurement of fundamental physical effects.”
Initiated and led by Olga Kocharovskaya at Texas A&M University, the project—funded by the U.S. National Science Foundation—holds promise for delving into gravitational time dilation at sub-millimeter distances. This capability could enable studies of relativistic effects on length scales previously beyond reach.
John Gillaspy, NSF program director for Atomic, Molecular, and Optical Experimental Physics, aptly notes, “This advance is both exciting and timely (double pun intended),” emphasizing the significance of this leap in precision timekeeping.