Precise representation of the J =3° energy levels of the m p n d and m s m p 3 configurations in Si  i , Ge  i , and Sn  i using a perturbed coupled-channel model

Results given demonstrate the ability of an energy-dependent coupled-channel model which includes a perturbation function to represent precisely (σ≤0.30 cm−1) all mpnd J=3° energy levels observed experimentally below the lowest ionization threshold for Si i, Ge i, and Sn i. In this model all energy dependence is placed into the closed-coupled μα parameters. The energy-independent Uiα elements of the frame transformation matrix are found to be close to those describing the transformation between pure LS- and jj-coupled states. Inclusion of corrections for perturbations which depend on the energy separation of a perturber level from the levels in the channels permits the quantitative inclusion of the msmp3 J=3° levels. To the authors’ knowledge these examples are the first to demonstrate the ability of coupled-channel models to reproduce entire, perturbed, strongly coupled multichannel- and multilimit-based excited electronic structures observed below the lowest ionization limit to within the average experimental uncertainties of the energy levels.