Cs133atomin

Cs133atomin refers to the cesium-133 atom, the stable isotope of the chemical element cesium (Cs). It has atomic number 55 and mass number 133, consisting of 55 protons and 78 neutrons in the nucleus. It is the only stable isotope of cesium, and natural cesium is essentially pure Cs-133; other cesium isotopes are radioactive and occur only in trace amounts or in artificial samples. In neutral form, a Cs-133 atom has 55 electrons arranged in the electron configuration [Xe] 6s1 and readily forms a Cs+ ion; as an alkali metal, cesium is highly reactive.

The most notable feature of Cs-133 is its role as the standard for the definition of the second. The hyperfine transition between the two ground-state levels of Cs-133 has a frequency of 9,192,631,770 Hz, and this frequency defines the second in the International System of Units. Atomic clocks that use cooled and manipulated Cs-133 atoms achieve extremely precise timekeeping, and cesium fountain clocks are among the primary time standards used by national metrology institutes.

Beyond timekeeping, Cs-133 serves as a reference in various metrological applications, such as calibration of instruments and tests of fundamental physics. Its stability and well-understood properties make it a common standard for spectroscopy and mass spectrometry calibration.

In summary, Cs-133 is the stable, natural form of cesium responsible for the world’s time standard and widely used as a precision measurement reference in science and industry.