The Nuclear Moments ofSe79

Microwave measurements of the $J=2\ensuremath{\rightarrow}3$ rotational transition of OCSe containing the radioactive-nucleus ${\mathrm{Se}}^{79}$ have established the ${\mathrm{Se}}^{79}$ spin as $\frac{7}{2}$ and the ${\mathrm{Se}}^{79}$ quadrupole moment as 0.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$\ifmmode\pm\else\textpm\fi{}20 percent. The quadrupole coupling constant $\mathrm{eqQ}$ is 752.09\ifmmode\pm\else\textpm\fi{}0.05 Mc/sec. The magnetic moment of ${\mathrm{Se}}^{79}$ has been determined as -1.015\ifmmode\pm\else\textpm\fi{}0.015 nuclear magnetons by observation of the Zeeman splitting of one hyperfine component. The $\frac{7}{2}$ spin and the large positive $Q$ are inconsistent with the single-particle nuclear-shell model, but suggest the configuration ${{({g}_{\frac{9}{2}})}^{2}}_{\frac{7}{2}}$. This assignment is substantiated by the negative magnetic moment.Measurement of isotopic shifts gives a value for the ${\mathrm{Se}}^{79}$ mass, and an odd-even mass difference of 2.4 millimass units for this nucleus.