Exposure of polyethylene and polystyrene to xenon difluoride (XeF2) in the presence of vacuum ultraviolet (VUV) irradiation emitted from O-2, N-2, Ar, Kr and Xe electrical discharges gives rise to surface fluorination. The extent of reaction is found to be governed by the synergistic effect between the VUV absorption characteristics of the XeF2 feed gas and the polymer substrate. Polystyrene in combination with krypton electrical discharge emission lines yields the most fluorinated surface. (C) Koninklijke Brill NV, Leiden, 2011