The hyperfine structure of the arc spectrum of columbium has been examined under conditions of high resolving power. The line patterns of $\lambda \lambda 4059$, 4080, 4117, 4137, 4168, 4649, 4672, 4675, 5344 and 6661 have been studied in detail. Three relatively independent methods have been used to determine the nuclear mechanical moment, $\frac{I^{*}h}{2\pi }$. All three methods indicate a value of $\frac{9}{2}$ for $I$, the quantum number of nuclear spin. Using the formulas given by Goudsmit, the nuclear $g$-factor has been calculated to be $g_I=0.83\mathrm{}$. This gives for the nuclear magnetic moment ${\mu }_I=3.7\mathrm{}$ nuclear magnetons.

• Received 18 September 1934

DOI:https://doi.org/10.1103/PhysRev.46.806