M1-transitions of Ti-like highly charged ions

Ground-term fine-structure levels and their magnetic-dipole (M1) transition properties of titanium-like ions are investigated theoretically through the atomic number Z=37-103. An anomalous stability in wavelength of J=3-2 M1-transition reported by Feldman (1991) is explained in terms of a concept of the critical atomic number beyond which the relativistic nature dominates in the corresponding fine-structure. The Tokyo-EBIT facility (1996) enabled us to observe the corresponding line in the visible range for Xe+32 and Ba+34 ions. The measured wavelengths are consistent with measurements by the NIST group (1995), however there remains a considerable discrepancy from present calculations. (orig.)