Correlation effects on fine-structure energy levels and oscillator strengths in Fe X

Fine-structure energy levels and oscillator strengths (OS’s) for some allowed transitions in Fe X are studied using extensive configuration-interaction (CI) wave functions, with relativistic effects incorporated through the Breit-Pauli Hamiltonian. The inclusion of crucial correlation effects arising from the two-electron excitation configurations 3s²3p³3d² and 3s3p⁴3d² in the CI expansion resolves all but two of the energy discrepancies between a recent calculation and experiment. Our OS’s agree excellently with the NIST data, but significant disagreements with other calculations call for further investigations.