We have examined the absorption and resonance Raman spectrum of mass-selected transition metal tetramers sputtered from a Ti-Cu alloy and deposited in an Ar matrix at 10 K. For the tetramers Ti4-nCun, we observed only a single Raman progression in approximately 300 cm(-1). This progression is most likely the totally symmetric stretch. The resolution of our mass-selection filter is insufficient to separate the tetramers, but from the isotopic Raman intensities we infer that the species observed in the Raman spectrum is TiCu3. Since only one progression was observed, sufficient information to determine the structure was not obtained. (C) 2004 Elsevier B.V. All rights reserved.