Photons from nuclear clock transition are seen at long last

Amazing stuff! Mind boggling! Clocks can never be precise enough! Better clocks lead to better theories and new discoveries.

Towards the next generation of atomic clocks!

"... The most accurate clocks today are based on optically trapped ensembles of atoms such as strontium or ytterbium. Highly stable lasers are locked into resonance with the frequencies of specific atomic transitions, and the laser oscillations effectively behave like pendulum swings – albeit with much higher frequencies and therefore greater precision. These clocks can be stable to within 1 part in 1020, which means that they will be out by just 10 ms after 13.7 billion years of operation – the age of the universe. ...
In search of ever greater precision and deeper insights, in 2003 ... proposed that a clock could be produced by interrogating not electronic energy levels of atoms but nuclear energy levels. ...

Such a nuclear clock would be extremely well isolated from external noise. “An atom is something like 10-10 m [across]; a nucleus is something like 10-14 or 10-15 m,”... “The nucleus is a much smaller antenna for the environment and is thus much less prone to shifts.”

A nuclear clock might therefore be an excellent probe of hypothetical, very tiny temporal variations in the values of fundamental constants such as the fine structure constant, which quantifies the strength of the electromagnetic interaction. Any such changes would point to physics beyond the Standard Model. ..."

"Atomic clocks are the world’s most precise timekeepers. Based on periodic transitions between two electronic states of an atom, they can track the passage of time with a precision as high as one part in a quintillion, meaning that they won’t lose or gain a second over 30 billion years – more than twice the age of the Universe. 
In a paper published today in Nature, an international team at CERN’s nuclear physics facility, ISOLDE, reports a key step towards building a clock that would be based on a periodic transition between two states of an atomic nucleus – the nucleus of an isotope of the element thorium, thorium-229. ...
“ISOLDE is currently one of only two facilities in the world that can produce actinium-229 isotopes,” ..."

From the abstract:

"The radionuclide thorium-229 features an isomer with an exceptionally low excitation energy that enables direct laser manipulation of nuclear states. It constitutes one of the leading candidates for use in next-generation optical clocks. This nuclear clock will be a unique tool for precise tests of fundamental physics. Whereas indirect experimental evidence for the existence of such an extraordinary nuclear state is substantially older, the proof of existence has been delivered only recently by observing the isomer’s electron conversion decay. The isomer’s excitation energy, nuclear spin and electromagnetic moments, the electron conversion lifetime and a refined energy of the isomer have been measured. In spite of recent progress, the isomer’s radiative decay, a key ingredient for the development of a nuclear clock, remained unobserved. Here, we report the detection of the radiative decay of this low-energy isomer in thorium-229 (229mTh). By performing vacuum-ultraviolet spectroscopy of 229mTh incorporated into large-bandgap CaF2 and MgF2 crystals at the ISOLDE facility at CERN, photons of 8.338(24) eV are measured, in agreement with recent measurements and the uncertainty is decreased by a factor of seven. The half-life of 229mTh embedded in MgF2 is determined to be 670(102) s. The observation of the radiative decay in a large-bandgap crystal has important consequences for the design of a future nuclear clock and the improved uncertainty of the energy eases the search for direct laser excitation of the atomic nucleus."

Photons from nuclear clock transition are seen at long last – Physics World The first direct measurement has been made of a thorium-229 nuclear transition that could potential

ISOLDE takes a solid tick forward towards a nuclear clock (primary news source) The observation at CERN’s nuclear physics facility of a long-sought decay of the thorium-229 nucleus in a solid-state system is a key step towards a clock that could outclass today’s most precise atomic clocks

Observation of the radiative decay of the 229Th nuclear clock isomer (no public access)

The ISOLDE facility at CERN