We report absorption ("scattering depletion") spectra and Raman measurements on niobium containing matrix samples prepared by the mass-selected ion deposition technique. Niobium dimer ions, produced by sputtering, were mass-selected with a Wien filter and codeposited with Ar and electrons. Several new dimer absorptions are identified in regions which were previously obscured by intense atomic transitions. Two absorptions are also observed in the region 580 - 720 nm, including a vibrational progression with w_e' = 426 (4) cm^-l. The Raman excitation profile closely mimics the dimer absorption spectrum. Raman spectre give w_e" = 420.5 (5) and w_ec_e" = 0.5 (3) cm^-l, in good agreement with previous measurements made in Kr matrices.

The absorption ("scattering depletion") and Raman spectra for Nb₃ in an argon matrix prepared by the mass selected ion deposition technique have been measured. The absorption spectrum in the visible region shows three overlaping bands, centered at 20,313 cm^-1, 18,786 cm^-1 and 17,036cm^-1, respectively. Resonance Raman spectra obtained with excitation into these bands give two distinct fundamental frequencies at 227.4(29)cm^-1 and 334.9(28)cm^-1 . The excitation profile of the two Raman fundamentals bears a strong resemblance to the absorption spectrum, but is "contracted" (ca. 900cm^-1) from both sides. The ratio of the two fundamental frequencies is close to sqrt(2):1, which indicates that the molecule has D_3h symmetry in the ground state and we assign the vibrations 227.4 cm^-1 to e' and 334.9cm^-1 to a.