Quantum mechanical study of the ¹⁶O + ¹⁸O¹⁸O → ¹⁶O¹⁸O + ¹⁸O exchange reaction: Integral cross sections and rate constants

The isotopic exchange reaction, ¹⁶O + ¹⁸O¹⁸O → ¹⁶O¹⁸O + ¹⁸O, involving excited ozone, $O3*$⁠, as intermediate complex, was investigated by means of a time independent quantum mechanical approach using the TKTHS potential energy surface (PES) [V. G. Tyuterev et al., J. Chem. Phys. 139, 134307 (2013)] of ozone. State-to-state integral cross sections were calculated for collision energies lower than 0.4 eV. Then specific and thermal rate constants were computed between 10 K and 350 K using these cross sections. The full quantum thermal rate constant is found to be in better agreement with the most recent experimental data than with previous studies where other O₃ PESs were employed, confirming therefore the higher accuracy of the TKTHS PES. However, the present theoretical thermal rate constant still remains below the measured rate, maybe due to the neglect of non-adiabtic couplings.