Hyperfine pumping and the measurement

Much larger differences of populations between the different hyperfine levels can be created by suitably altering the relative intensities of the hyperfine components of the pumping lamp. Since these components are very close together conventional interference filters cannot be used, but fortunately in many cases the natural displacement between the resonance lines of different isotopes of an element enables selective light sources to be constructed. This is especially true in mercury, as shown by Table 16.1, and in the case of rubidium which we consider now. 

The energy levels and hyperfine structure of resonance line of rubidium at 7947 X are shown in Fig.18.6 for 

F=2 of the Rb atoms in the cell will decrease while the population of the lower level F=1 increases. 

In either case the resulting population difference enables the hyperfine magnetic resonance transitions AF = 1 to be detected when microwave power at 6835 MHz is fed into the optical pumping cell. Analagous techniques can be used to 

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. 

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