The dissociative electroionization of ammonia and ammonia-d3. I. The NH+ and NH2+ dissociation channels

Locht, Robert; Servais, Christian; Ligot, M.; Derwa, F.; Momigny, J.

doi:10.1016/0301-0104(88)87053-8

Cited by 35 publications

(36 citation statements)

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“…However, in the H + dissociation channel, onsets are measured at both energies of 34.9 ± 0.4 and at 39.2 ± 0.2 eV [ 9] proving that the Franck-Condon region simultaneously crosses the attractive well and the repulsive part of both the potential energy surface of the X l A 1 and of the Ã 1 E states of NH 3 2+ .…”

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confidence: 92%

“…As the overall shape of these curves would suggest, the third double ionization energy of NH 3 could be masked by autoionization. However, the dissociative ionization of NH 3 leading to NH + and H + and/or H 2 + shows thresholds respectively at 46.8, 46.1, and 47.2 eV in the corresponding ionization efficiency curves [9]. On the contrary, no critical energy is measured around 46 eV for N + [9].…”

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confidence: 93%

“…All quantum-mechanical calculations agree to describe the NH 3 2+ ground state by the X 1 A 1 symmetry obtained by removal of two 3a 1 electrons. Although stable toward dissociation, this state is found to be dissociative over a long time scale by both PIPICO [3] as well as by electroionization [5,9]. When the former experiment measured coincidences between NH 2 + and H + ions [3], in the latter an appearance energy at about 35 eV is measured for both the NH 2 + and the H + ions [9].…”

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confidence: 95%

“…When the former experiment measured coincidences between NH 2 + and H + ions [3], in the latter an appearance energy at about 35 eV is measured for both the NH 2 + and the H + ions [9]. Furthermore, H 2 + ions are produced at the same energy [9].…”

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confidence: 96%

“…This work is still in progress [9]. The doubly ionized species, observed in the mass spectrum of NH 3 , are included in this work.…”

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confidence: 99%

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The double ionization of ammonia. Its dissociation into the doubly ionized fragment N2+

Locht

Momigny

1987

Chemical Physics Letters

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The double ionization and dissociation of NH 3 into the doubly ionized fragment N 2+ is investigated by electron impact. Two double ionization energies of NH 3 are directly measured at 34.8 ± 0.2 and 39.4 ± 0.5 eV. A third critical energy observed at 66 eV is assigned to a NH 3 2+ state whose ionization energy is at 61 eV. Two appearance energies are observed for the N 2+ ion at 65.9 ± 1.7 and 74.3 ± 2.6 eV. The translational energy distribution of N 2+ is shown to be essentially thermal. The former onset is ascribed to the dissociation of the 61 eV state of NH 3 2+ , the latter originates from a doubly ionized NH 3 2+ state at 70 eV.Compared to the literature dedicated to ionization and dissociation of molecular cations, the abundance of work devoted to double ionization is very small. This statement has to be ascribed to the generally low abundance of double ionized species. Until recently, only electron impact and high-energy ion impact allowed us to observe these species. The improvement of high-energy light sources, e.g. He (II) resonance lamps, and even more the increasing number of electron synchrotron radiation facilities, allowed us to reach photon energies far above the 21.22 eV energy limit. These developments were the starting point of an increasing number of publications in the field of double and even multiple ionization.During the last few years, the double ionization of NH 3 has been studied by several techniques including double charge transfer spectroscopy (DCTS) [ 2+ into singly as well as doubly ionized fragment ions. The dissociation of doubly charged NH 3 into pairs of singly charged ions has recently been studied by photoionization using the photoion-photoion coincidence (PIPICO) technique [3]. Several theoretical calculations have been devoted to the NH 3 dication, using a variety of techniques [1,[6][7][8].The aim of this work was to investigate the double ionization of NH 3 , as well as its dissociation, as a complementary source of information for the detailed study of the dissociative ionization of NH 3 and ND 3 in the 15-45 eV energy range. This work is still in progress [9]. The doubly ionized species, observed in the mass spectrum of NH 3 , are included in this work.The experimental apparatus and the experimental conditions used in the course of this work have been described in detail elsewhere [10]. At the present time the instrument is fully computer controlled [11], The ammonia and ammonia-d 3 , purchased from Air Liquide and Merck, Sharp & Dohme respectively, are distilled under high vacuum to reduce the traces of water in the samples. Special care is taken to reduce the background signal of N + and O + by prolongated bake-out at 250° C. Owing to the low intensity of the signals, each first differentiated ionization efficiency curve was scanned 600-700 times, requiring 20-30 h. This operation was repeated at least 10-15 times. The onset energies reported in this work are averaged values from these 10-15 independent measurements. The error limits mentioned are the standard devia...

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confidence: 92%

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confidence: 93%