Intercombination Line Oscillator Strengths in the Helium Isoelectronic Sequence

The ratios of oscillator strengths for transitions into the 1s2 iS0 ground state from the 1s2p 1P1 and 1s2p 3P1 states, respectively, are calculated for helium and helium4ike ions through Ne ix using an energy matrix which includes spin-orbit and spin-spin interactions. The desired ratio is expressed principally in terms of term values deduced from some observed - ,1,2 transitions. Such observations for 0 vii are reported here. Oscillator strengths for the intercombination transition are deduced using calculated values for the transition. The results are useful in interpreting soft X-ray line radiation from such transitions as observed in the solar corona as well as in high-temperature laboratorygenerated plasma.