Measurement of the electric quadrupole moments of $^{26-29}$Na

The nuclear electric quadrupole moments of the isotopes $^{26}$Na, $^{27}$Na, $^{28}$Na and $^{29}$Na were measured by $\beta$-NMR spectroscopy in single crystals of LiNbO$_3$ and NaNO$_3$. High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear laser beam.The polarized nuclei were implanted into the crystals and NMR signals were observed in the $\beta$-decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of $^{27-31}$Na and confirmed the spin $I=3/2$for $^{31}$Na. The results are discussed in comparison with large-basis shell-model calculations.