The Nuclear Moments ofTa181

An analysis of the hfs pattern of several Ta II lines has made it possible to determine the separations of the three levels of the hfs multiplet associated with the $5d^{3}6s{}_{}{}^5{}_{}{}^{}F_1^{}{}_{}{}^{}$ state of Ta II. For this multiplet, the constants $A$ and $B$ appearing in the energy expression $W=W_J+\frac{1}{2}AK+BK(K+1\mathrm{})\mathrm{}$ have the numerical values $A=(-0.079\mathrm{}\pm 0.001)$ ${\mathrm{cm}}^{-1\mathrm{}}$ and $B=(-0.77\mathrm{}\pm 0.4)\times {10}^{-3\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Calculations are carried out in order to evaluate the magnetic and quadrupole moments of the ${\mathrm{Ta}}^{181}$ nucleus. On the basis of the above measurements the magnetic moment as calculated by the Goudsmit-Fermi-Segrè formula has the value of 1.9 nuclear magnetons. Taking into account effects due to the spatial extension of the nucleus, this result is raised to 2.1 nuclear magnetons when the correction factor of 12 percent as listed by Klinkenberg is applied. The result for the quadrupole moment as calculated by the Casimir formula is +5.9×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$. According to Sternhermer this moment should be increased by a factor of 10 percent in order to include the effect of an induced quadrupole moment in the closed shell electrons. With this correction the quadrupole moment has the value of +6.5×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$.