We report on the absorption, resonance Raman, and Raman excitation profile spectra of mass selected lutetium dimers in argon matrices. Two broad absorption regions were found between 415 and 545 nm with peaks at 418, 433, 452, 472, 505, 540 nm, and between 635 and 660 nm with peaks at 640 and 652 nm. Resonance Raman spectra were obtained by excitation into one of these regions with the visible light of an Ar ion laser between 458 and 514 nm. Two progressions were assigned to lutetium dimers. We interpret them to represent two distinct electronic states: A ground-state X and an excited state A. For the ground (X) state, we obtain omega (e)=121.6 +/-0.8 cm(-1) with omega (e)x(e)=0.16 +/-0.10 cm(-1), leading to a spectroscopic dissociation energy of 2.9 +/-1.8 eV, and force constant k(e)=0.76 +/-0.01 mdyne/Angstrom. The lowest excited electronic state (A) has an origin at 210.7 cm(-1) and almost identical vibrational parameters. Comparison of spectroscopic properties of lanthanide dimers is discussed, and evidence is presented that lutetium should occupy the position normally given to lanthanum in the periodic table.