The far ultraviolet absorption spectrum of oxygen has been photographed under high dispersion in the region 1300-650A. The bands are explained as going to the various excited states of $\mathrm{O}_2^{}{}_{}{}^{+}$ as limits and are attributed to the removal of $v\pi$, $\omega \pi$ and $x\sigma$ electrons, respectively, from the normal state of ${\mathrm{O}}_2$. The results strongly support Mulliken's assignment of the visible $\mathrm{O}_2^{}{}_{}{}^{+}$ bands to the transition ${}_{}{}^4{}_{}{}^{}{\Sigma }_g_{}^{-}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$. The distances of the ${}_{}{}^4{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}{\Sigma }_g_{}^{-}{}_{}{}^{}$ states of $\mathrm{O}_2^{}{}_{}{}^{+}$ from the ground state of ${\mathrm{O}}_2$ are given as 16.1 and 18.2 volts, respectively, with possible errors of about a tenth of a volt. The appearance and nonappearance of strong electronic series going to known ionization potentials are also discussed.

• Received 8 August 1935

DOI:https://doi.org/10.1103/PhysRev.48.714