Low-energy electron impact excitation of the water molecule

Complex-Kohn calculations of electron impact excitation of the water molecule are reported. We consider electronic excitation to singlet and triplet states arising from promotion of the electrons in the highest occupied orbitals to the lowest lying virtual orbitals which have substantial Rydberg character. Some of the resulting states are expected to be dissociative. An analysis of the effects of interchannel coupling is given, and several different close-coupling expansions of the trial wave function are used. In particular, the validity of the electric-dipole coupling criterion for predicting strong electron-impact excitation is examined