Nuclear Electric Quadrupole Moment ofNa23by the Atomic Beam Resonance Method

The hyperfine structure of the $n=3\mathrm{}{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{} \mathrm{and} {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ excited atomic states of ${\mathrm{Na}}^{23}$ have been investigated using a modification of the atomic beam resonance method. The $C$ region is illuminated with resonance radiation from a sodium discharge lamp which brings some of the atoms into the excited levels where they have lifetimes of the order of ${10}^{-8\mathrm{}}$ sec. The application of an rf field of an appropriate frequency causes transitions among the excited state hyperfine levels and "scrambles" the populations of these levels. Since the atoms are essentially "tagged" by the deflection which they have undergone in the $A$ field, this "scrambling" will cause a change in the refocused intensity at the detector.