Theoretical Study of the Temperature- and Pressure-Dependent Rate Constants for Nine Reactions between CO n ( n = 0-4), O m ( m = 1-3), C 2 O, and C 3 O 2 during the Radiolysis of Carbon Dioxide.

We investigate the reaction pathways of nine important CO 2 -related reactions using the revDSD-PBEP86-D3(BJ)/jun-cc-pV(T+d)Z level and simultaneously employ an accurate composite method (jun-Cheap) based on coupled-cluster (CC) theory. Subsequently, the Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) is solved to calculate the temperature- and pressure-dependent rate constants. This work investigates reactions involving transition states that have been overlooked in previous literature, including the dissociation of singlet-state C 3 O 2 , the triple channel formation of C 2 O + CO to form C 3 O 2 , and the formation of O 3 + CO. The results show that CO 3 is highly prone to dissociation at high temperatures. Finally, the kinetic data show that over a wide temperature range, our calculations are consistent with previous experimental measurements. The majority of the reaction rate constants studied exhibit significant pressure dependence, while the O 3 + CO reaction is pressure-independent at low temperatures. These results are instrumental in the development of detailed kinetic models for the CO 2 radiolysis reaction network.