A study of the metastable and long-lived Rydberg fragments resulting from electron impact on NH3

Abstract

The production of long-lived, excited fragments following electron-impact dissociation of ammonia has been investigated using the technique of translational spectroscopy. Over an impact energy range from threshold to 200 eV, the dominant species observed were hydrogen 2s and Rydberg atoms. Through extensive time-of-flight and excitation function measurements of these fragments, five dissociation channels were found to contribute to the production of the H(2s) atoms, while the H(RYD) signal was found to consist of hydrogen atoms resulting from at least four distinct processes. Threshold and kinetic energy measurements show that for most of these processes a substantial amount of the bombarding electron’s energy is channeled through the unobserved product or products of the dissociation. In addition to the hydrogen features, a low intensity group of fragments which we believe are long-lived nitrogen Rydberg atoms was identified in the time-of-flight spectra. Excitation function measurements indicate that two dissociation channels contribute to the production of these fragments. When possible, the present results are compared to previous measurements of the dissociative excitation and ionization of ammonia.