Absorption spectra of Si-2, Ge-2, and Sn-2, observed between 50 and 5000 cm(-1) is neon and argon matrices at 4 K, were assigned to the lowest (3) Pi(u) <-- X (3) Sigma(g)(-) electronic transition. In all three cases, the Franck-Condon envelope of vibrational bands allowed T-00, omega(e)’, omega(e)’x(e)’ to be determined. In the Si-2 molecule [near Case (a)] T-00 = 313 cm(-1) and each vibrational band was split into Omega triplets (0,1,2) in the upper state. A Zeeman effect on these lines was detected in magnetic fields-up to. 4 T As the spin-orbit coupling becomes larger in Ge-2 and Sn-2, the 1(u) <-- X0(g)(+) transition [case (c)] was observed, and the corresponding parameters in the upper state determined. For Sn-2 the magnetic-dipole 1(g) <-- X0(g)(+) transition was also detected and identified by the splitting-and broadening of the band in magnetic fields up to 4 T. The results are discussed in the context of the ab initio calculations and other experimental results on these molecules.