Saturation Studies of N2− in Irradiated Sodium Azide

Saturation studies of N₂⁻ in sodium azide (NaN₃) were performed at temperatures of 4.2° and 2°K and at a frequency of 9 GHz. The product $T_1{T}_2$ was found to be approximately 10⁻¹¹ sec². The assumption that the width of the partially resolved hyperfine structure is equal to the width of the homogeneously broadened packet allowed estimations of $T_2$ as 10⁻⁸ sec and $T_1$ as 10⁻³ sec. This assumption, justified in the text, also allowed one to calculate an upper limit on the ratio $\mathrm{(a)}$ of the homogeneous to inhomogeneous linewidths of 0.07. The saturation data yielded values of 0.4–0.8 for this ratio. The spin‐diffusion time, $T_{21}$ , was shown to be the order of 10⁻⁵ sec, so that spin diffusion was a dominant relaxation mechanism. This was used to explain apparent ambiguities in the values of $a$ . The relaxation times were highly anisotropic when the dc magnetic field was nearly parallel to the crystalline $c$ axis. Further experiments are needed before one can understand this variation.