The absorption (scattering depletion) spectrum and resonance Raman spectrum for Ru-2 ill an argon matrix prepared by the mass-selected ion deposition technique have been obtained. The absorption spectrum in the Visible region shows a single broad transition centered at 470 nm. Resonance Raman spectra, obtained by excitation into this band with dye laser radiation, display a single sharp progression with Lines at 343.8(26) cm(-1), 681.6(32) cm(-1), 1017.5(26)cm(-1), 1350.2(25) cm(-1),and 1678.9(8) cm(-1). These data give omega(e) = 347.1 +/- 0.9 cm(-1) with omega(e)x(e)= 1.85 +/- 1.5 cm(-1) leading to a spectroscopic dissociation energy of 2.0 +/- 0.2 eV, Sidebands in the Raman spectra are indicative of a weak coupling (Huang-Rhys factor, S similar to 0.1-0.7) between the dimer and the phonons of the argon host.