Knowledge Bank

The H$2${--}O$_2^{-} (X $2$\Pi) complex has been examined using the coupled-cluster theory at the CCSD(T)/aug-cc-pVDZ and CCSD(T)/aug-cc-pVTZ levels. Electronic structure calculations show that the global minimum energy structure corresponds to a planar bent geometry with a well depth of 1550 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. For this geometry, the distance between centers of masses of moieties of the complex is 2.57{\AA}, angstroms and the angles between the internuclear axes of the superoxide radical and the hydrogen molecule with respect to the axis that connects their centers of masses are $104irc$ and $165irc$ , respectively. These results indicate that the hydrogen molecule and the superoxide radical are held together by a strong hydrogen bond within the complex. Results of the current work will be discussed and compared to results of our recent ab initio study of the H$2${--}O$2$ (X $3$\Sigma) complex.