Sodium atoms have been oriented by means of circularly polarized resonance radiation. The amount of orientation agrees with that calculated from the intensity of the light source used. The polarization of the light scattered from the sodium sample varies in the expected manner when the light intensity and applied magnetic field are varied. Illumination with unpolarized resonance radiation is shown to result in alignment of the sodium atoms. The largest degree of orientation achieved corresponds to an average value for the nuclear, electronic, and total angular momenta of ikfj = 0.180 = 0.1207, Ms = 0.035 = 0.0705, M^ = 0.216 = 0.108F, respectively.

A SUBSTANTIAL quantity of strongly polarized atoms could serve as a source of oriented nuclei for nuclear physics experiments, as a source of polarized electrons, or, because of the enormously enhanced signal, as an interesting material for microwave spectroscopy and nuclear magnetic resonance experiments. Kastler 1 has suggested that circularly-polarized resonance radiation will polarize atoms. This polarization effect results from the fact that there is a fairly large probability that the angular momentum carried by the absorbed photon is retained by the atom in the emission process. Bitter and Brossel 2 have looked for this polarization with negative results, and more recently Brossel, Kastler, and Winter 3 have obtained a positive result. On the other hand, Bitter, Lacey, and Richter 4 have reported a negative result. We have obtained a polarization of sodium vapor which is in agreement with the expected value. The energy level diagram including the hyperfine structure and a typical set of transitions produced by the scattering of resonance radiation is shown in Fig. 1. Note that on the average MF is greater after the scattering.A schematic view of the apparatus is shown in Fig. 2. A sodium beam was used only because this is a convenient way of guaranteeing that the contamination by foreign gas is insignificant. The transverse components of the earth's magnetic field are roughly balanced out by a set of coils. An additional magnetic field H along the axis of the system (direction of incident light) could be varied as a parameter. As a means of detecting whether the sodium beam has been polarized, the plane-polarization ratio of the scattered light is measured. Figure 3 shows a plot of the polarization ratio of the scattered light vs the magnetic field applied along the axis defined by the incident beam. The dip at 0.12 gauss is explained by the fact that this is the field necessary to balance this component of the earth's field. With zero magnetic field along the axis, a small residual transverse component of the magnetic field serves to mix the MF states destroying the polarization. The asymmetry about 0.12 gauss is probably caused by the rather large inhomogeneities in the axial magnetic field. The polarization effect is intensitydependent indicating a multiple-photon effect. The form of the dependence indicates an essentially 2-photon effect.Observations on the light source showed that for curve A, Fig. 3, the two lines of the doublet had about the same_peak in-FIG. 1. Energy level diagram of sodium with a sample of the transitions involved, in this case transitions via the &P\F -2 states.

Doppler free spectroscopy was performed on the 7p1/2 and 7p3/2 states in neutral cesium-133 using a frequency doubled titanium sapphire laser stabilized to a temperature-stabilized ultra-low expansion optical cavity. The absolute frequencies for the centers of gravity of the two states were determined to be cm−1 and cm−1, factors of 500 and 650 better than previously reported measurements, respectively. The magnetic dipole and electric quadrupole constants were measured to be MHz for the 7p1/2 state and MHz and MHz for the 7p3/2 state, which are consistent with previously published values.

We report on the calibration of a temperature stabilized ultra-low expansion (ULE) cavity using previously measured molecular tellurium and atomic cesium lines. By means of a dual frequency modulation technique, the frequency dependence of the free spectral range of the ULE cavity is measured and was found to vary by less than 60 Hz over the ∼55 THz range of the calibration. This method of calibration enables the ULE cavity to measure absolute frequencies to better than 1.5 MHz.

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