Rydberg isotope shift

A measurement of the 1S-2S frequency alone can therefore give only a modest further improvement of the Rydberg constant before its interpretation is limited by other uncertainties. At one time it has been suggested to determine the proton-electron mass ratio from the 1S-2S isotope shift. However, after the most recent measurements by VAN DYCK et al. [37], the uncertainty of the isotope shift is now dominated by nuclear size effects. 

The use of autoionizing Rydberg levels converging to excited states of the ion to determine ionization potentials has been discussed above. If autoionization resonances as narrow as those found in gadolinium exist in the actinides, it should be possible to determine the isotope shifts and hfs of such features. (isotope shifts for actinides range up to 0.4 cm l per mass unit and odd atomic number actinides exhibit hfs with total widths of 4 to 6 cm l and hfs component spacing of 0.2 cm l or more for some transitions). 

In this section I hope to show how the sensitivity of laser spectroscopy is exploited to obtain data on very low concentrations of atoms. In particular I will start off by considering a few laser atomic beam studies aimed at measuring optical isotope shifts and show how short-lived nuclei can be studied in this way. I shall also mention how it is possible to beat the natural linewidth and obtain supernatural spectra . The discussion of laser studies at low atomic concentrations then leads me onto consider experiments on laser cooling and trapping of atoms and ions. In this context I will also mention some experiments using the shelved electron idea to detect very weak transitions. Finally, I will say something about Rydberg atoms and the effects of atoms near metallic surfaces. 

Figure 1. Experimental setup for hyperfine structure and isotope shift measurements of Ba Rydberg states. (Taken from Ref. 28.)...

In this section we review isotope shift and hyperfine structure measurements concerning the even-parity Rydberg series msns and msnd 0 of Ca, Sr, and Ba, which have been studied most extensively up to now. Hyperfine interactions occurring in msns S Rydberg states can be readily understood and will be considered first. 

Figure 32 compares displacements of the F = / component of Ba observed for 5q and Rydberg states. In the upper part (Figure 32a) open circles represent the experimental isotope shifts " Ba of the transitions 6s So 6sns Sq, corrected for the normal mass contribution. The lower part (Figure 32b) displays experimental data (open circles) derived... 

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. 

Hypetfine Structure and Isotope Shifts of Rydberg States of Other Two-Electron Systems... 

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