Experimental manifestations and uses

The black body shifts are not confined to Rydberg atoms, but also alter the frequency of atomic clock transitions. Itano et al. have shown that the Cs 9 GHz ground state hyperfine interval, the definition of the second, is increased by one part in 1014 when the temperature is raised from 0 K to 300 K.29. 

As shown by Table 5.2, at 300 K the n = 17 and n = 18 black body decay rates are =5 X 104 s-1, which might seem tolerable. However, in even slightly dense 

Stoneman and Gallagher have used black body radiation to make precise measurements of the avoided crossings between the K ns and n — 2 Stark manifold states in electric fields,36 and these measurements are described in Chapter 6. 

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