The absorption and Raman spectra for nickel dimers in an argon matrix prepared by the mass-selected ion deposition technique have been measured. A weak dimer absorption band is centered around 480 nm. Resonance Raman spectra obtained from exciting into the dimer 480 nm band show a vibrational progression for which w(e) = 259.2 +/- 3.0 cm(-1) with w(e)x(e) = 1.9 +/- 0.7 cm(-1). The dinickel Raman spectra are discussed in terms of isotopic shifts, as well as the changeover from d-d bonding to s-s bonding along the series Fe-2-->Cu-2.