content_image/415618.jpg content_image/415617.jpg content_image/415626.jpg content_image/415627.jpg content_image/415628.jpg
<img src='content_image/415618.jpg'>

transition. For the first stage the intensity over the 10 nm bandwidth was varied from ≈ 22 W/cm 2 to ≈ 5 W/cm $^{2}$. Data were taken at cell temperatures corresponding to saturated vapor pressures of 0.15, 1.05, 3.9, and 8.5 mPa. The dependence of the center-of-gravity on the varied parameters is shown in Fig. 14 and are summarized in Table I. 

As with the previous transitions there was no signifi- cant shift arising from the light power. A linear fit gave a slope of − 23(62) kHz /P , where P is the normalized operating power. This gives us an uncertainty of 85 kHz in the center-of-gravity frequency. We found uncertain- ties in the hyperfine A and B constants of 11 kHz and 458 kHz, respectively. 

Unlike the other transitions studied here, we did ob- serve a dependence of the center-of-gravity on the mag- netic field (Fig. 14). There was clear evidence of broad- ening in the peaks at the largest magnetic fields. We attribute the shift to a break down of the line-shape model as the line broadens coupled with the overlap of the peaks. In this case, we base our estimate of the uncer- tainty on the difference of the point taken at the zeroed field with the residual field and find an uncertainty of 

<img src='content_image/415617.jpg'>

35 kHz in the optical frequency. There is no evidence for a dependence of the extracted hyperfine A constant, and w e find a magnetic-field uncertainty of 6 kHz for it. For th e B constant we find an uncertainty of 125 kHz. 

We see no clear evidence for any temperature depen- dent effects. Using the larger of standard deviation or the uncertainty in the mean, we find uncertainties of 7 kHz, 1 kHz, and 38 kHz for the temperature-dependent uncer- tainties of the center-of-gravity frequency, the hyperfine A constant, and the hyperfine B constant, respectively Applying these uncertainties we find 

We have used the technique of velocity-selective two- photon excitation to measure the center-of-gravity fre- quencies and the hyperfine coupling constants for the 8S$_{1}$$_{/}$$_{2}$ , 9S$_{1}$$_{/}$$_{2}$ , 7D$_{3}$$_{/}$$_{2}$ , and 7D$_{5}$$_{/}$$_{2}$ states of Cs. The results for all of the transitions are summarized and compared to other published experimental values in Table II. This technique has potential metrological applications for sec- ondary frequency standards at optical wavelengths. At a more fundamental level, the hyperfine coupling measure- ments are valuable in improving atomic structure calcu- lations. The measurement accuracy of multiple transi- tions at significantly different wavelengths rivals that of 

<img src='content_image/415626.jpg'>

<img src='content_image/415627.jpg'>

<img src='content_image/415628.jpg'>

## V. CONCLUSIONS 

