Experimental and theory studies of the oxidation reaction of neutral gold carbonyl clusters in the gas phase

► Neutral gold carbonyl clusters are detected by single photon ionization. ► Reactions of Au3(CO)2 and Au3(CO)3 clusters with O2 are thermodynamically favorable. ► Relativistic effects are important for gold cluster calculations. ► A catalytic cycle is proposed for CO oxidation to CO2 on Au3.