Hyperfine Structure of Atomic Nitrogen

Abstract

The hyperfine structure of the ground state of ${\mathrm{N}}^{14}$ and ${\mathrm{N}}^{15}$ has been determined by optical pumping with spin exchange. A circulation system, which forced the nitrogen through an electrodeless rf discharge into the resonance bulb, provided a continuous source of atomic nitrogen. Optically-pumped cesium was used to polarize and analyze the nitrogen. The zero-field intervals extrapolated to zero pressure are ${\mathrm{N}}^{14}$, $\nu (\frac{5}{2}-\frac{3}{2})=26\mathrm{}127288\pm 40$ cps; ${\mathrm{N}}^{14}$, $\nu (\frac{3}{2}-\frac{1}{2})=15\mathrm{}676390\pm 40$ cps; and ${\mathrm{N}}^{15}$, $\nu \mathrm{}(2-1)=29\mathrm{}290902\pm 40$ cps. The hyperfine constants are $A^{14}=(+)10450925\pm 20$ cps, $B^{14}=(-)7\pm 20$ cps, and $A^{15}=(-)14645441\pm 20$ cps. These results include small corrections for second-order hyperfine interactions. A pressure shift of + 1.9±0.4 cps/mm Hg of ${\mathrm{N}}_2$ was established for the ${\mathrm{N}}^{14}$ magnetic dipole interaction constant ($A^{14}$). The hyperfine structure anomaly is $\Delta =\left(\frac{A^{14}{g_I}^{15}}{A^{15}{g_I}^{14}}\right)-1=+(1.002\mathrm{}\pm 0.004)\times {10}^{-3\mathrm{}}$. The effect of spin-orbit and spin-spin mixing of the ${}_{}{}^4{}_{}{}^{}S$, ${}_{}{}^2{}_{}{}^{}D$, and ${}_{}{}^2{}_{}{}^{}P$ states is discussed.