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(Horology) an atomic clock based on the frequency of inversion of the ammonia molecule
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
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|Noun||1.||ammonia clock - an atomic clock based on vibrational frequency of the nitrogen atom in the ammonia molecule|
atomic clock - a timepiece that derives its time scale from the vibration of atoms or molecules
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