Theoretical calculation of energy levels and spectra ab nitio are described forinitio transitions of the type pm-pm-1l, especially 3pm-3pm-13d transitions in the Ar I and Cl I isoelectronic sequences. Strong changes of wvavefunction composition occur in going from neutral atoms to ions as a result of collapse of the 3d wavefunction; for m = 2 and 6 these take the form of coupling changes, and for m = 3-5 they take the form of changes of parentage composition. Abnormally low Ti v 3p6-3p54d intensities are explained as an interference effect in evaluation of the dipole radial integral.
ROBERT D. COWAN, "Theoretical Study of pm-pm-1l Spectra," J. Opt. Soc. Am. 58, 924-932 (1968)