- Rubidium standard
A rubidium standard is a
frequency standardin which a specified hyperfine transitionof electrons in rubidium-87 atoms is used to control the output frequency. A rubidium standard consists of a gas cell, which has an inherent long-term instability. This instability relegates the rubidium standard to its status as a secondary standard.
All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6 834 682 610.904 324 Hz. The amount of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1% when the rubidium vapor in the resonance cell is exposed to microwave power near the transition frequency. The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an RF synthesizer (referenced to the crystal) through the transition frequency.
* [http://tf.nist.gov/general/enc-re.htm#resonancefrequency NIST Time & Frequency A-Z Glossary - Resonance Frequency]
* [http://www.npl.co.uk/server.php?show=ConWebDoc.1727 Secondary Representation of the SI Second]
* [http://www.ptb.de/en/org/4/44/441/info2_e.htm PTB "Unit of Time"]
Federal Standard 1037Cand [http://tf.nist.gov/general/enc-re.htm#resonancefrequency NIST]
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