Resonance phenomena in electron impact excitation of the fundamental vibrational modes of water

Absolute differential cross-sections for electron impact excitation of the bending (010) and unresolved stretching (100)+(001) vibrational modes of water (H2O) are reported. The incident electron energy is E0=7.5 eV and the scattered electron angular range 10°–120°. Significant angular structure in both the (010) and (100)+(001) differential cross-sections, due to resonant decay from H2O−, is apparent. This observation confirms the earlier result of Seng and Linder [J. Phys. B 9 (1976) 2539] for resonance enhancement of the stretching modes, but is contrary to their analysis for the bending mode where they postulated the dominant population mechanism was due to direct scattering. Integral cross-sections for excitation of the (010) and (100)+(001) quanta at 7.5 eV are also reported.