Fine structure and differential metastability measurements for the doubly excited 1s2s2p ${}^4$$P^o$ and 1s2$p^2$ ${}^4$P states of lithiumlike Ne viii

Fine-structure intervals have been measured for the J=(1/2), (3/2), and (5/2) levels of the doubly excited 1s2s2p ${}^4$ $P^O$, and 1s2$p^2$ ${}^4$P terms of lithiumlike Ne viii, using fast-ion-beam spectroscopy in the far uv. In addition, lifetimes for the J=(1/2) and (3/2) levels of the upper term were determined, and their comparison with theory shows the importance of choosing for such levels atomic models which include magnetic interactions. Our measurement for the J=(3/2) level of 1s2$p^2$ ${}^4$P is in excellent agreement with a recent relativistic calculation and removes a previous discrepancy between measured and theoretical values for this level.