Word: cesium
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Dates: during 1980-1989
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...inside atoms. Ramsey's so-called separated oscillatory fields technique did not just become a valuable scientific tool; it also provided the basis for modern-day atomic clocks. Like the ticking of a pendulum in a grandfather clock, the rapid-fire (9,192,631.770 times a second) oscillations of cesium-atom nuclei, spinning like tops inside a magnetic field, can be used to pace off time...
...make these measurements, a beam of atoms, usually cesium, is sent through an oscillating magnetic field, which reverses the spin on the atoms' electrons...
Ramsey's procedure is so precise that the number of times the nucleus of a cesium atom rotates now can be measured with an accuracy of one part in a trillion...
...Ramsey's increased precision that enabled scientists to use the atomic clock for the official measurement of world time. In 1967, his method was used to redefine the second as the length of time it takes a cesium nucleus to rotate 9,192,631,770 times...
...dangerous pollution, and 75 FBI agents are currently there looking for proof of fraud in the disposal and incineration of plutonium-laden wastes. But what has environmental officials most puzzled is something they never expected to find even at trouble-prone Rocky Flats: traces of radioactive strontium and cesium that a nuclear chain reaction could produce -- even though there is no nuclear reactor at the site. The Environmental Protection Agency has demanded a study to determine how the mysterious isotopes got to Rocky Flats...