Nuclear clocks are showing the benefits of escaping from scientific silos

A frequency comb to search for dark matter in the thorium-229 atoms using a time-resolved laser system

Nuclear clocks might soon be just as accurate as the atomic ones, a testament to the value of competition and cooperation in research.

But theoretical models of the nucleus cannot predict the energy of such transitions with the necessary accuracy, so finding this one meant searching an enormous range of possible values. Moreover, thorium-229 decays slowly from its first energy state. So, with a half-life of around 30 minutes, the chance of observing the decay from second to second is low.

Atomic clocks currently hold the world record for most accurate timekeeping. They tick out time through the frequency of light emitted and absorbed by electrons jumping between atomic energy levels. Lasers that are locked to a clock give the read-out.

Nuclear clocks are 100 million times more sensitive to the effects of dark matter than atomic ones, because of the amplified nuclear transition frequencies. The latest result is so precise it can narrow down the possible energy ranges in which light dark matter could exist. Nuclear physics could also benefit from the more precise transition frequency, which could help scientists to distinguish betweendifferent possible shapes of the throrium-229 nucleus, she adds.

A team from JILA used a system known as a frequency comb to look for the transition frequencies in the trillions of thorium-229 atoms. The comb has regular and even spacing. It allows researchers to illuminate the crystal with many precise frequencies at once to look for a match, rather than scanning laboriously through the range of possible options using a single-frequency laser.

Observing the transition for the first time “felt amazing”, says study co-author Chuankun Zhang, a physicist at JILA. “We spent the entire night doing all the tests to check if this is actually really the signal that we were looking for,” he says.

honing is needed for the laser system. Kocharovskaya is a physicist at Texas A&M University in College Station. The source in the future clock will be a Prototype.