RELATIVE INTENSITIES OF 2S(2)2P (2)P-2S2P(2) S-2, P-2 TRANSITIONS IN B-LIKE IONS OF OXYGEN THROUGH CHLORINE

The 2s2p2 S-2(1/2) and P-2(1/2) levels in the boronlike ions are strongly affected by spin-orbit interaction, which leads to intermediate coupling, and the degree of the deviation from pure LS coupling varies with the nuclear charge of the ions. We have measured the relative intensities of the decays from the nominal 2s2p2 S-2(1/2) level to the 2s(2)2p P-2(1/2,3/2)0 fine structure levels of the ground term, for all elements from O to Cl. This ratio would be 1 divided-by 2 for pure LS states, but it clearly deviates from this value in the range of our study. We also discuss the measured relative intensities of the 2s2p2 P-2(1/2,3/2) decays. We compare our results with predictions from various calculations involving configuration mixing with electrons up to the n = 3 shell. Our own MCHF calculations indicate that an additional inclusion of n = 4 electrons has no significant effect on the transitions of interest.