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The cesium atomic clock at the NBS Radio Standards Laboratory generates the second-the SI unit ol time. A quartz-oscillator-controlled microrcave signnl is held at 9,192,631,770 Hz by continuous comparison with the cesium-133 resonance at that frequency. A beam of cesium-133 atoms passes lejt to right thruugh the long metal
Cesium is the best choice of atom for such a measurement because all of its 55 electrons but the outermost are confined to orbits in stable shells of electromagnetic force. Thus, the outermost electron is not disturbed much by the others.
Frequency offset can be measured in either the frequency domain or time domain. A simple frequency domain measurement involves directly counting and displaying the frequency output of the DUT with a frequency counter. The reference for this measurement is either the counter’s internal time base oscillator, or an external time base (Fig. 17.3).
In this paper, we report on a precise measurement of the lifetime, τ D,ofthe52D 5/2 state of cesium. We use a standard technique known as time-resolved single-photon counting. Our measurement yields a lifetime value of 1353(5) ns, in agreement with the predictions by Safronova et al. [16,18]. The paper is organized as follows: in Sec. II, we ...
The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms is used to control the output frequency.
A measurement is a direct or indirect comparison of a certain quantity with an appropriate standard or unit of measurement. The value of a physical quantity is the quantitative expression of a particular physical quantity as the product of a number and a unit, the number being its numerical value.
The two most widely used atomic clocks in recent years have been the cesium beam atomic clock and the rubidium clock. Such clocks have provided the accuracy necessary to test general relativity and to track variations in the frequencies of pulsars.
