Domination of dissociative double-electron excitation over dissociative single-electron excitation in electron collisions with NH3

Double-electron excitations in electron collisions with NH3 are investigated in the range of the outer valence and inner valence excitations by means of angle-resolved electron-photon coincidence measurements. Double-electron and single-electron excitations are termed double and single excitations, respectively, in this article. It is found that the dissociative double excitation resulting in H(2p) formation becomes more dominant over the dissociative single excitation at 100-eV incident energy as the electron scattering angle increases just from 8 degrees. to 15 degrees. This remarkable domination is not expected from the independent particle model and strongly supports the double-excitation mechanism through the electron correlation induced by the penetration of the incident electron depth into the valence orbitals of a NH3 molecule.