gtensor for substitutional nitrogen in diamond

We report a measurement of an axially symmetric g tensor for the substitutional nitrogen center in type-IIa synthetic isopure ¹²C diamond. Because the nitrogen concentration of the diamond studied is exceptionally low the electron-paramagnetic-resonance linewidth is sufficiently narrow to reveal the g-tensor anisotropy. Studies of the angular dependence reveal [111] symmetry and an axial g tensor in which gₚₑᵣₚ-g_∥=0.0001±{}0.000 03. From the narrow linewidth, we observe that the deviation from the [111] symmetry exhibited by the nitrogen center is less than 0.5^∘{}.