Combined measurements of ion probe and optical emission spectroscopy have been employed to investigate the propagation of LaMnO3 ablation plasma in oxygen background gas. The expansion dynamics as a function of the background pressure shows a transition from a free-plume, at low pressures, to a shock-wave-like expansion, at larger pressures. Plume splitting is observed in a pressure range which depends on the distance from the target surface. The distance-related pressure dependencies for the different expansion regimes have been rationalized in the frame of a simple model of plume propagation into the background gas. (c) 2005 Elsevier B.V. All rights reserved.