Hyperfine intervals

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. 

Fig. 7.7. Schematic of the Yale experiment to measure the hyperfine interval of ground state positronium. On the left there is an overall view of the apparatus, whilst the right-hand figure shows the microwave cavity and gas cell in which the positronium is formed. 

Mills Jr., A.P. (1983c). Line-shape effects in the measurement of the positronium hyperfine interval. Phys. Rev. A 27 262-267. 

The hydrogen maser, operating at the frequency of this ground state hyperfine interval, remains one of the most stable frequency standards, as shown in figure 2, especially at short time intervals. For practical reasons, one has chosen to define the unit of time, the second of the Systeme International, in terms of the analogous hyperfine structure interval, about 9 GHz, in the ground state of the Cs atom... 

Concerning strictly the measurement of hyperfine intervals, these two techniques maintain their useful role and many results have... 

Therefore, the ratio of the hyperfine interval to the A-doubling interval depends on the combination F = a" p- gnuc- Higher-order corrections modify this parameter to F = a i V - nuc [64],... 

Consider a diatomic molecule with a ground state (one unpaired electron). Examples of such molecules include LaS, LaO, LuS, LuO, and YbF [74]. The hyperfine interval Ahfs is proportional to a ZF rei(aZ)pgnuc. where Frei is an additional relativistic (Casimir) factor [76]. The rotational interval Arot a p is approximately... 

The method of quantum beats has found application in the measurement of fine structure intervals, polarizabilities, and hyperfine intervals in several species. The basis of the approach is to prepare a coherent superposition of at least two states by pulsed excitation and observe the subsequent... 

In this chapter we shall be concerned mainly with the principles of the technique, the effect of relaxation processes, and magnetic resonance transitions between Zeeman sub-levels. We shall therefore initially describe the experiments in terms of the populations of the ground state sub-levels. The discussion of the effects of phase coherence (Hertzian coherence) and experiments involving transverse pumping is reserved until section 17.8. Moreover the application of optical pumping methods to the investigation of hyperfine intervals and the measurement of nuclear moments is postponed until Chapter 18, as are the applications of this technique in devices such as magnetometers, atomic clocks, and masers. 

In fact the frequency of these field-dependent transitions can be used to make an exact evaluation of the quadratic term in equation (18.29), thus leading to a precise measurement of Vf pg. In these experiments the imcertainty in the measured field values leads to a relative error in the determination of the hyperfine interval of Av /v jpg 10 provided that the effects of the light and pressure shifts discussed below are eliminated. 

Atom Nuclear spin Hyperfine interval Vp pg Reference... 

Thus, in addition to the extrapolation to zero intensity of the pumping light which must be made to eliminate systematic errors due to the light shifts discussed in section 17.9.7, a further extrapolation of the measured hyperfine resonance frequencies to zero buffer-gas density must be made. Zero-field hyperfine intervals measured by the optical pumping method are listed in Table 18.3, together with a selection of the results obtained by the atomic beam technique. Generally the optical pumping results are more precise than the older atomic beam results. The table... 

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