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 ${\mathrm{N}}^{14}$, $\ensuremath{\nu}(\frac{5}{2}\ensuremath{-}\frac{3}{2})=26127288\ifmmode\pm\else\textpm\fi{}40$ cps; ${\mathrm{N}}^{14}$, $\ensuremath{\nu}(\frac{3}{2}\ensuremath{-}\frac{1}{2})=15676390\ifmmode\pm\else\textpm\fi{}40$ cps; and ${\mathrm{N}}^{15}$, $\ensuremath{\nu}(2\ensuremath{-}1)=29290902\ifmmode\pm\else\textpm\fi{}40$ cps. The hyperfine constants are ${A}^{14}=(+)10450925\ifmmode\pm\else\textpm\fi{}20$ cps, ${B}^{14}=(\ensuremath{-})7\ifmmode\pm\else\textpm\fi{}20$ cps, and ${A}^{15}=(\ensuremath{-})14645441\ifmmode\pm\else\textpm\fi{}20$ cps. These results include small corrections for second-order hyperfine interactions. A pressure shift of + 1.9\ifmmode\pm\else\textpm\fi{}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 $\ensuremath{\Delta}=(\frac{{A}^{14}{{g}_{I}}^{15}}{{A}^{15}{{g}_{I}}^{14}})\ensuremath{-}1=+(1.002\ifmmode\pm\else\textpm\fi{}0.004)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The effect of spin-orbit and spin-spin mixing of the $^{4}S$, $^{2}D$, and $^{2}P$ states is discussed.