New Fine Structure in Neutral Oxygen

Untabulated fine structure in O I has been resolved in the triplet multiplets $\lambda 8446(3s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-3p{}_{}{}^3{}_{}{}^{}P_{210}^{}{}_{}{}^{})$, $\lambda 2884(3p{}_{}{}^3{}_{}{}^{}P_{21}^{}{}_{}{}^{}-3\mathrm{}{d}^{\prime }{}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{})$, and $\lambda 4368(3s{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-4p{}_{}{}^3{}_{}{}^{}P_{210}^{}{}_{}{}^{})$. Interferometer patterns of these lines were analyzed to obtain splittings and relative intensities. Listed as a doublet, $\lambda 8446$ has three components whose relative intensities allowed establishment of the $3p{}_{}{}^3{}_{}{}^{}P_{210}^{}{}_{}{}^{}$ anomalous splitting as follows: $J=1\mathrm{}$ lies 0.559(±0.003) ${\mathrm{cm}}^{-1\mathrm{}}$ below $J=2\mathrm{}$, and $J=0\mathrm{}$ lies 0.158(±0.002) ${\mathrm{cm}}^{-1\mathrm{}}$ above $J=2\mathrm{}$, in agreement with Edlén. $\lambda 2884$, heretofore found single, has two components, separated by 0.558(±0.002) ${\mathrm{cm}}^{-1\mathrm{}}$. Two components of $\lambda 4368$, previously considered single, were resolved and found to have a separation of 0.300(±0.001) ${\mathrm{cm}}^{-1\mathrm{}}$, the weaker component having the shorter wavelength. From the relative intensities it is deduced that $J=0\mathrm{}$ lies above the degenerate $J=2, 1$ level of the state $4p{}_{}{}^3{}_{}{}^{}P_{210}^{}{}_{}{}^{}$, which, like $3p{}_{}{}^3{}_{}{}^{}P_{210}^{}{}_{}{}^{}$, is perturbed by an unobserved state in the displaced (${}_{}{}^2{}_{}{}^{}D$) system.