Cesium133overgång

The Cesium133overgång, often referred to as the cesium-133 hyperfine transition, is the fundamental basis for the modern definition of the second. It describes a specific electronic transition within a neutral atom of cesium-133. This transition occurs between two energy levels of the atom's ground state, specifically the two hyperfine levels of the F=4 and F=3 states of the 6s electron. The frequency of the electromagnetic radiation emitted or absorbed during this transition is extremely stable and reproducible. This stability makes it an ideal reference for timekeeping.

The exact frequency of the Cesium133overgång is defined as 9,192,631,770 Hertz. This means that 9,192,631,770 oscillations of the electromagnetic wave associated with this transition correspond to one second. Atomic clocks, such as those used by national metrology institutes and for global positioning systems, utilize this phenomenon to maintain incredibly precise time. The remarkable stability of this atomic transition is due to the fact that it is largely unaffected by external factors like temperature, pressure, or magnetic fields, which can influence other timing mechanisms. Therefore, the Cesium133overgång serves as the international standard for defining the second, underpinning our global system of time measurement.