DEFININGCONSTANT: hyperfine transition frequency of Cs
- PID: si:definingconstant:caesium_transition_frequency:2019
- Definition: The unperturbed ground state hyperfine transition frequency of the caesium 133 atom, ΔνCs, is exactly 9 192 631 770 Hz.
- Source: SI Brochure 9th Ed. 2019, p 127
9 192 631 770 Hz
- Numerical Value: 9192631770
- Unit: Hz
- Unit in Base SI: s-1
- This value was fixed by the CGPM in 1967 (Resolution 1) and reiterated by the CGPM in 2018 (Resolution 1).
- The caesium transition frequency is an atomic parameter which may be affected by the environment, such as electromagnetic fields. However, the underlying transition is well understood, stable and a good choice as a reference transition under practical considerations.
- Related Definitions
- hasConstantSymbol -> ΔνCs