The Absorption Spectrum of Atomic Sodium

Abstract

Using a long optical path attained by the method of Kratz and Mack, the wave-lengths of the principal series of sodium in absorption have been measured to $n=73\mathrm{}$, and observed to $n=79\mathrm{}$. The members to $n=9\mathrm{}$ have been resolved. The series limit has been computed to be 41449.65±0.02 ${\mathrm{cm}}^{-1\mathrm{}}$ from the center of gravity or 41449.69±0.02 ${\mathrm{cm}}^{-1\mathrm{}}$ from the lower hyperfine structure component, of the $3s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ term. Forbidden $3s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-\mathrm{nd}{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2},\frac{5}{2}}^{}{}_{}{}^{}$ were found up to $n=13\mathrm{}$. A critically compiled table to all known levels, including $\mathrm{np}{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^{}{}_{}{}^{}$ to $n=73\mathrm{}$ and $\mathrm{nd}{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2},\frac{5}{2}}^{}{}_{}{}^{}$ to $n=13\mathrm{}$, is given. The pressure shift from a foreign gas is less than reported by some earlier observers.