Fine structure of the 1s2s2p 4P/sup o/ and 1s2p24P doubly excited states in lithiumlike carbon, nitrogen, and oxygen

The fine structure of the 1s2s2p 4P/sup o/-1s2p24P multiplet in the doubly excited quartet system of three-electron C IV, N V, and O VI has been measured using the method of beam-foil spectroscopy. The fine-structure splittings have been determined to within approx. 5 cm-1 in both the upper and lower states of each ion, and the absolute transition wavelengths have been measured to within approx. 0.1 A (approx. 10-3 eV). The wavelength results show that existing relativistic and nonrelativistic energy separations calculated for these 4P states are inaccurate by approx. 1% for Z = 6--8, and that calculations of the fine-structure splittings are inaccurate by (10--20) % for 1s2s2p 4P/sup o/ and by > or approx. = 20% for 1s2p24P. Lifetimes have also been measured for the J = 5/2, 3/2, and 1/2 levels of 1s2p24P. Differential metastability is found to be a characteristic feature of these core-excited fine-structure states in all three ions. Comparison with calculated autoionization and K x-ray transition rates for Z = 7 and 8 indicates that the 1s2p24P/sub 5/2/ lifetime is determined essentially by its autoionization rate to the doublet continuum through magnetic interactions, whereas the J = 3/2 and 1/2 states decay at a slower rate that is more characteristic of the 4P/sup o/-4P radiative transition rate