Ab initio study of the HO₂+NO reaction: Prediction of the total rate constant and product branching ratios for the forward and reverse processes

The PES for the HO₂+NO reaction was elucidated at the G2M(CC1)/6-311+G(3d,2p) level of theory. The rate constants for the forward and reverse processes were calculated under different conditions. The results show that the formation of HO+NO₂ from HO₂+NO is pressure-independent below 10 atm; the decomposition of HOONO to HO+NO₂ is more favorable than its isomerization to HONO₂ due to the high barrier for the latter process. The reverse reaction HO+NO₂→HONO₂ (HOONO) appears to be strongly pressure-dependent. All the predicted results agree closely with experimental values.