Atomic Frequency Standards

Abstract

From tracking the movement of celestial bodies to mechanical clocks and now prevalent atomic clocks, timekeeping has been one of the greatest quests for finding stable and better oscillators. Measurement of transition frequency between two designated levels of an atom forms the basis of atomic clocks. Time is derived from the measurement of frequency and that is the reason that atomic clocks are more appropriately called atomic frequency standards. Since the realization of first atomic frequency standard based on cesium in 1955, the field of precision time and frequency metrology has been revolutionized. Along with the evolution of timekeeping, a detailed description of various types of atomic frequency standards, applications, and the roadmap toward redefinition of SI second is presented in this chapter.KeywordsTimekeepingAtomic ClocksCesium fountainOptical clocks