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, Xe⁺³² through U⁺⁷⁰, 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 (Nd⁺³⁸) and Gd (Gd⁺⁴²) 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.