The optical transmission of an optically oriented sodium vapor in spin-exchange equilibrium with atomic nitrogen has been used to measure the zero-field hyperfine splitting of ${\mathrm{N}}^{14}$ and ${\mathrm{N}}^{15}$. The ground state of atomic nitrogen is ${}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{}$. For ${\mathrm{N}}^{14}$, which has $I=1\mathrm{}$, $\Delta {\nu }_{\frac{5}{2}\to \frac{3}{2}}=26.12721\mathrm{}\pm 0.00018 \mathrm{Mc}/sec,$ $\Delta {\nu }_{\frac{3}{2}\to \frac{1}{2}}=15.67646\mathrm{}\pm 0.00012 \mathrm{Mc}/sec.$ For ${\mathrm{N}}^{15}$, which has $I=\frac{1}{2}$, $\Delta \nu =29.29136\mathrm{}\pm 0.00016 \mathrm{Mc}/sec.$

The nuclear moments of ${\mathrm{N}}^{14}$ and ${\mathrm{N}}^{15}$ have been remeasured by observing the effect of saturating the nitrogen resonance on the proton resonance in N${\mathrm{H}}_4^{+}$. The results were $\frac{g\left(14\right)\mathrm{}}{g\left(H^1\right)}=0.072\mathrm{}23695\pm 0.00000008,$ and $\frac{g\left(15\right)\mathrm{}}{g\left(H^1\right)}=-0.101\mathrm{}33093\pm 0.00000008.$

The ${\mathrm{N}}^{14}$—${\mathrm{N}}^{15}$ hyperfine anomaly obtained by combining these measurements is $\Delta =\frac{\frac{A\left(15\right)\mathrm{}}{A\left(14\right)\mathrm{}}}{\frac{g\left(15\right)\mathrm{}}{g\left(14\right)\mathrm{}}}-1=0.000\mathrm{}983\pm 0.000017.$

A short discussion of the mechanism of spin-exchange collisions is given.

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