We report on the effect of Xe buffer gas on the C2(d̃3IIg→ã3II u) emission which results from the excimer laser-induced multiphonon fragmentation of acetylene, triethylenediamine (Dabco), and benzene. We find that, upon addition of Xe, normal quenching of this emission occurs for 248-nm (KrF) photolysis of the above molecules, while an unusual enhancement is found for 193-nm (ArF) photolysis. Other radical emissions resulting from the same process, e.g., CH(Ã2Δ→X̃2II) and CN(B̃2Σ+→X̃2Σ +), show normal quenching at both wavelengths. The possible mechanisms of this unusual enhancement are discussed. © 1982 American Chemical Society.861322712273