Moreover, nuclear binding is stronger that its atomic counterpart, so the shifts between energy levels are higher in energy and would be resonant with higher-frequency lasers, making a smaller change detectable. Any such changes would point to physics beyond the Standard Model. “The nucleus is a much smaller antenna for the environment and is thus much less prone to shifts.”Ī 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. “An atom is something like 10 -10 m a nucleus is something like 10 -14 or 10 -15 m,” explains Sandro Kraemer of KU Leuven in Belgium, who was involved in this latest research. Such a nuclear clock would be extremely well isolated from external noise. In search of ever greater precision and deeper insights, in 2003 Ekkehard Peik and Christian Tamm of Physikalisch-technische Bundesanstalt in Braunschweig, Germany proposed that a clock could be produced by interrogating not electronic energy levels of atoms but nuclear energy levels. These clocks can be stable to within 1 part in 10 20, which means that they will be out by just 10 ms after 13.7 billion years of operation – the age of the universe.Ītomic clocks are not just great timekeepers, physicists have used them to study a range of fundamental phenomena such as how Einstein’s general theory of relativity applies to atoms confined in optical traps. 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. The most accurate clocks today are based on optically trapped ensembles of atoms such as strontium or ytterbium.
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