We describe optical spectroscopy diagnostics of UV laser ablated rare earth-Ni-2-B-2-C superconducting targets. In the light of this characterization. we have optimized the parameters for high-quality thin film deposition of borocarbide compounds. Our measurements have evidenced relevant differences in the flow velocity as well as in the spatial divergence of different plasma components. This is related to the influence of the different masses of the atoms of the multicomponent target during plume expansion. These results have led us to identify the target-to-substrate distance and substrate temperature as the critical parameters for the deposition of high-quality thin films, as clearly evidenced by residual resistivity ratio measurements. (C) 2002 Elsevier Science B.V. All rights reserved.