Estimate of the Nuclear Moment ofNi61from Electron Spin Resonance

The electron spin resonance spectra of nickel and cobalt have been studied in single crystals of MgO. Hyperfine structure was detected from the ${\mathrm{Ni}}^{61}$ isotope in the spectrum of ${\mathrm{Ni}}^{+2\mathrm{}}$ and the hyperfine splitting constant $A^{61}$ found to be (8.3±0.4)×${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. X irradiation of cobalt-containing crystals results in the formation of ${\mathrm{Co}}^{+1\mathrm{}}$ (isoelectronic with ${\mathrm{Ni}}^{+2\mathrm{}}$). The hyperfine splitting constant $A^{59}$ is (54.0±0.2)×${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Comparison between $A^{59}$ and $A^{61}$ yields a value of 0.30±0.02 nm for the nuclear moment of ${\mathrm{Ni}}^{61}$.