The most accurate time pieces available today are based upon an electronic transition between two energy levels in the cesium atom. With appropriate electronic tools, this transition is utilized to produce clocks that are accurate to 3 parts in 10
"Time to Trap an Ytterbium Ion'' by Pauline Rigby,
Nature 386, p 225 (1997), reports that a new electronic transition has been measured in atoms of the element ytterbium that will make possible the construction of clocks that are three orders of magnitude (1000 times) more accurate than cesium clocks.These clocks depend upon fluorescence, the tendency for some of the excited states of atoms to have long lifetimes before decaying into lower energy states. Electrons in these atoms become temporarily trapped in higher energy levels. A result of the Heisenberg uncertainty principle is that the longer the lifetime of an electronic transition, the more precisely its energy can be measured. Molecular clock precision depends upon this measurement. The newly observed transition in ytterbium has a lifetime of about ten years, making it difficult to detect but also ideal for high precision time measurement.
Scientists are excited about this development because, after the necessary engineering has been completed, it may extend their ability to measure a fundamental parameter by
three orders of magnitude - a very great improvement.
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Vol. 24, No. 9
Newsletter: Access to Energy Newsletter Archive Volume: Issues Issue/No.: Vol. 24, No. 9 Date: May 01, 1997 01:10 PM (For actual publication date see newsletter.) Title: Science and Humility
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