AnomalousZdependence of a magnetic dipole transition in the Ti I isoelectronic sequence

In isoelectronic sequences, transition wavelengths ordinarily move rapidly to shorter wavelengths as Z increases. However, it has been predicted that a particular sequence of magnetic dipole (M1) transition wavelengths for the Ti-like ions, ${\mathrm{Xe}}^{+32\mathrm{}}$ through ${\mathrm{U}}^{+70\mathrm{}}$, remain relatively constant in the 320–400-nm range. In the present paper we extend the experimental identifications of the Ti-like M1 transitions from Ba and Xe to Nd (${\mathrm{Nd}}^{+38\mathrm{}}$) and Gd (${\mathrm{Gd}}^{+42\mathrm{}}$) to verify this behavior. Using the newly acquired wavelengths to adjust atomic parameters, we have also calculated improved wavelengths for all such M1 transitions between Xe (Z=54) and Os (Z=76). © 1996 The American Physical Society.