NIST researchers have developed a mercury atomic clock that is at least five times more precise than the current national standard clock based on cesium atoms. The experimental clock, which measures the oscillations of a single mercury ion held in an ultra-cold electromagnetic trap, produces “ticks” at optical frequencies, allowing time to be divided into smaller units and increasing precision. The current version of NIST-F1, the national standard clock, would neither gain nor lose a second in about 70 million years, while the latest mercury clock would maintain accuracy for about 400 million years.
The improved mercury clock incorporates several technical advancements, including better control of systemic perturbations, compensation for the irregular shape of mercury’s electron cloud, and reduced frequency shift caused by magnetic fields. The clock’s accuracy is made possible by comparing its optical ticks to the primary cesium standard, NIST-F1, and using an optical frequency comb to convert the optical ticks to microwave frequencies for counting.
While optical atomic clocks have the potential to be more stable and accurate than current cesium-based clocks, they remain a long way from being accepted as international standards. Research groups around the world would need to agree on an atom and clock design, and a system of additional optical clocks would be required for continuous timekeeping.
Source: https://www.nist.gov/news-events/news/2006/07/mercury-atomic-clock-keeps-time-record-accuracy
Keywords: atomic, ion, frequency, precision, accuracy
