Using matrix-isolation infrared spectroscopy and DFT calculations, the reactions between 532 nm pulsed laser-ablated Ta and CO2 in argon gas ambient have been investigated. The major reaction products trapped in solid argon were found to be neutral OTaCO and O2Ta(CO)(2) the anions OTaCO- and O2Ta(CO)(2)(-). The observed absorption bands of the reaction products were identified by isotopic substitution and reproduced well by DFT calculations of vibrational fundamentals. Upon irradiation with a pulsed laser at 355 nm, the neutral OTaCO and O2Ta(CO)(2) were enhanced while O2Ta(CO)(2)(-) and C2O4- anions disappeared in the measured IR spectra. The potential energy surfaces of the interactions of Ta with CO2 and CO2- were calculated, and the insertion of Ta into CO2 was suggested to proceed via electron transfer from Ta to CO2, in which CO2- formation plays an important role in the activation of inert CO2 molecules.