Isotope shift hyperfine-induced

Figure 27. Experimental (A) and calculated (solid curve) hyperfine-induced isotope shifts (Taken from Ref. 60.)...

Figure 33. King diagram for unperturbed (upper part) and perturbed (lower part) 6sns Sq Rydberg states. Open symbols refer to experimental isotope shifts, solid ones to data corrected for hyperfine-induced singlet-triplet mixing. The modified isotope shifts shown in Figure 33 were obtained using the data plotted in Figure 32a. (Taken from Ref. 62.)...

Together with a (6sl8s So) = 0.67 (cf. Section 3.1.1) Eqs. (44) and (45) have been used to derive the solid circles shown in Figures 32 and 33 at n = 18. As can be seen from Eqs. (45) and (46), the hyperfine-induced isotope shifts are a direct measure of the Rydberg character of the So and Po states. The F = 7 component of the S level, however, experiences a total shift from the position predicted by the Lande interval rule caused by the interaction with both 7 = 0 states. Since the perturber Po lies below the S, state, both contributions are of opposite sign and fortuitously cancel. This is also evident from Figure 32b. 

One remark is due here about the validity of the King plot procedure, usually employed to check the consistency of isotope shifts in two different electronic transitions. The hyperfine-induced magnetic contribution to the isotope shift has the consequence, that shifts between pairs of even (1=0) nuclei and shifts between even and odd (l= =0) nuclei no longer lie on a straight line. However, after correcting for the hyperfine-induced shift, the validity of the linear relationship between the isotope shifts in two transitions is restored. Hence, any deviation from the King plot of shifts that involve odd nuclei can be taken as strong evidence for the existence of hyperfine-induced shifts. 

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