Doubly excited states of ammonia produced by photon and electron interactions

Abstract

The formation and decay of doubly excited ammonia produced by photon and electron interactions have been investigated through measuring (i) the cross sections for the emission of the Lyman-α fluorescence in the photoexcitation of NH3 as a function of incident photon energy in the range 15–60 eV and (ii) the electron-energy-loss spectrum of NH3 tagged with the Lyman-α photons at 100 eV incident electron energy and 8° electron scattering angle in the range of the energy loss 15–48 eV. Six superexcited states have been found, four of which are doubly excited states with one being a singly excited state and the other being a state including electron configurations of a single excitation and double excitations. There exist two forbidden doubly excited states whose widths are approximately 1 eV, i.e. much sharper than the allowed superexcited states in the electron-energy-loss spectrum tagged with the Lyman-α photons. It is remarkable that the electron interaction with NH3 at 100 eV incident electron energy and 8° electron scattering angle promotes the ratio of the oscillator strength for the double excitation to that for the single excitation as compared with the photon interaction.