Correlation effects important for accurate oscillator strengths

It is shown that the oscillator strengths for several transitions in He are more accurate in the MCHF than the HF approximation and that this improvement cannot be attributed to the charge distribution function. The important configurations are those which contribute significantly to the state under consideration and at the same time, have an allowed transition to the dominant configuration of the other state. Thus all external correlation may be important in the accurate determination of oscillator strengths.