Ab initio complex Kohn calculations of dissociative excitation of water

We report the results of close-coupling complex Kohn calculations of cross sections for electron-impact excitation of the water molecule into electronically dissociative states in the energy range from 8 to 30 eV. We have coupled five channels including the ¹A₁ ground state and excited singlet and triplet states formed by promoting the occupied 3a₁ and 1b₁ electrons to the lowest unoccupied 4a₁ orbital. These states have theoretical vertical energies in the range from 8 to 12 eV and are known to be dissociative. Our calculations have confirmed the existence of Feshbach resonances related to the A₁ and B₁ excited states which are responsible for dissociative attachment in water at rather high energies. We found that these resonances indeed correspond to configurations 3a₁4a₁² and 1b₁4a₁². Our results include both total and differential cross sections. We also make comparison between theory and available experimental data.