One of the components of the rubidium frequency measurement standards is the rubidium absorption cell. This is an unsoldered glass tank containing Rb87 vapour mixed with buffer gas.
The absorption cell has a minimum width of line O-O of Rb transition, the maximum signal-to-noise ratio at the optical indication of O-O transition, good reproducibility for transition frequency of not worse than 1∙10-10, and a small temperature coefficient not exceeding 3∙10-11 1/deg.
Short-term instability of the frequency of rubidium cells is:
1.5∙10-10 | at a measurement interval of 0.1 sec. |
5∙10-11 | at a measurement interval of 1 sec. |
1.5∙10-11 | at a measurement interval of 10 sec. |
3∙10-12 | at a measurement interval of 100 sec. |
2.5∙10-12 | at a measurement interval of 1 h. |