Improved potential function for HOO−/OOH− isomerization

The hydroperoxyl anion HO2− is a prototype for multidimensional proton transfer because of the low barrier to HOO−/OOH− isomerisation and the importance of the O atom dynamics. In this paper we report an analytic potential energy surface for HO2− constructed by fitting a potential function to 1859 ab initio data points computed at the QCISD(T)/6-311++G(2df,pd) level. The present potential function supersedes the one we reported previously [W.-T. Chan and I.P. Hamilton, J. Chem. Phys. 105 (1996) 5907]. The present functional form is considerably simpler than our previous one and should prove useful for similar triatomics and for further theoretical studies of multidimensional proton transfer.