Comment on ‘‘Relativistic excitation energies and oscillator strengths for the 6s21S0→6s6p1P1,3P1transitions in Hg-like ions’’

In a recent paper, Chou and Huang [Phys. Rev. A 45, 1403 (1992)] employ the multiconfiguration relativistic random-phase approximation (MCRRPA) in an attempt to remove discrepancies between experimental and theoretical oscillator strengths for the 6${\mathit{s}}^2$ ${}_{}{}^1{}_{}{}^{}$ ${\mathit{S}}_0$→6s6p ${}_{}{}^1{}_{}{}^{}$ ${\mathit{P}}_1$, ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_1$ transitions in mercurylike ions. Their MCRRPA results are found to be still in poor agreement with beam-foil measurements, and the authors suggest that a significant part of this disagreement may arise from ‘‘an improper account of the cascade effects in beam-foil lifetime measurements.’’ However, Chou and Huang have overlooked several, more recent beam-foil measurements in which ‘‘proper’’ account has been taken of cascading by the application of an arbitrarily-normalized-decay-curve technique with which their MCRRPA results are still in poor agreement. We conclude that this disagreement is mainly due to the omission by Chou and Huang from their calculation of core-polarization effects. In fact, calculations in which such effects are included show quite satisfactory agreement with the beam-foil measurements in which an account of cascade effects has been taken.