On the doubly ionized states of ammonia

Tarantelli, Francesco; Tarantelli, A.; Sgamellotti, Antonio; Schirmer, J.; Cederbaum, Lorenz S.

doi:10.1016/0009-2614(85)80305-5

Cited by 65 publications

(18 citation statements)

References 12 publications

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“…Table 2 allows us to compare the present data to the most recent experimental and theoretical results on the double ionization energies of NH 3 ·. For the first ionization energy good agreement is found, within the error limits, between the present results, double charge transfer [1], photoionization [3] and theoretical predictions [1,[6][7][8]. 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.…”

supporting

confidence: 84%

“…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].…”

mentioning

confidence: 99%

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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: 84%

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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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“…0kland et al (1976) reported open-shell SCF calculations of double zeta quality, while Tarantelli et al (1985a) have used ab initio Green's functions and configuration interaction methods. These results and the experimental findings of Shaw et al (1977) are given in Table 7.…”

Section: Auger Transition Energiesmentioning

confidence: 99%

“…The experimental Auger spectrum of water vapour has been measured by Siegbahn et al (1975). The double ionisation energies have been determined by ab initio methods using SCF procedures including limited CI (Hillier and Kendrick 1976; Agren et al 1975;Agren and Siegbahn 1980) and Green's function techniques by Tarantelli et al (1985b). In view of the many possible double-hole final states in a similar energy range electron correlation effects are very important in determining their energies.…”

Section: ·17 0·36mentioning

confidence: 99%

Auger Electron Spectra of Molecules: The First Row Hydrides

Larkins¹,

Tulea²,

Chelkowska³

1990

Aust. J. Phys.

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A semi-empirical molecular orbital approach primarily developed to predict the Auger energies and transition rates associated with complex polyatomic molecules has been evaluated by reference to the first row hydrides. For this suite of molecules, spanning a range of symmetry classes, high resolution experimental spectra and ab initio energy calculations are available for comparison. The method proposed provides a good first estimate for transition rates. Relative Auger energies are less satisfactory, especially when electron correlation effects are strong. Absolute kinetic energies are too low, principally due to the neglect of electronic relaxation. The usefulness of the approach is mainly for the interpretation of spectra for larger systems where ab initio calculations are not readily accomplished. A need for further experimental measurements obtained using photoelectron-Auger electron coincidence studies is identified to remove uncertainties associated with the extent of satellite contributions present in all the spectral profiles so far recorded. In the present work the satellite contribution to the methane Auger spectrum is estimated to be 16% of the total intensity compared with an earlier estimate in the literature of 49%.

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Diisocyanogen or Isocyanogen?

Cederbaum

Tarantelli

Weikert

et al. 1989

Angew. Chem. Int. Ed. Engl.

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M,im/zl __tFig. 2. LDI mass spectrum of glucose isomerase. Measured molecular weight: 172420. Sum of 30 single spectra.as well as a cluster ion (2w3@ with lower intensity. All signals can be used to improve mass determination precision. The fact that glucose isomerase, which consists of four noncovalently bound subunits, is desorbed at least predominantly, if not only as the intact protein is a further proof for the extreme softness of the matrix-UVLDI technique.The total sample amount deposited on the target was 500 fmol, spread over an area of several mm2. At least several thousand single spectra can be obtained from such a preparation. An estimate of the sample consumption per single spectrum gives ca. lo-" mo116] leaving much room for a further reduction of sample amount necessary.M,im/zl-Fig. 3. LDI mass spectrum of catalase. Measured molecular weight: 236230. Sum of 50 single spectra. Figure 3 shows the spectrum of catalase with a measured molecular weight of 236230, summed over SO single laser shots. Again, the molecular ion, ( M 4 ) @ , consisting of 4 equal subunits with a molecular weight of 59060 each, is clearly detected, as well as the doubly charged species (M4)20. Because of the absence of a triply charged molecular ion it can be concluded that the peak at m/z 59 060 originates from the singly charged subunit ( M I ) @ and not the quadruply charged molecular ion ( M J 4 @ . Correspondingly the signal at mjz 29 500 represents the doubly charged subunit ( M , ) * @ . Whether or not the protein mostly decayed into its subunits upon preparation (and evaporation of the solvent) already. or the decomposition was predominantly induced by or during the desorption process still needs further investigation.As in all desorption techniques sample preparation plays the key role in LDI of high mass molecules. Highly purified samples and the use of ultrapure water for protein and m a trix solutions is a prerequisite for a successful mass analysis, indicating that the salt contamination commonly present can disturb the homogeneity of the protein-matrix-association necessary for high mass ion desorption. Under such conditions, all spectra show a very good signal-to-noise ratio. Ths mass spectra shown are typical for matrix-UVLDI: so far no fragmentation of covalent bonds has been observed. The intense signals in the mass range below ca. 1000 Dalton are caused exclusively by the matrix. Whether a successive frag-mentation, which would most suitably be done by a second laser, enables sequencing of peptides and proteins comparably to Collision-Induced-Dissociation has yet to be investigated.While the stable cyanogen molecule (NCCN) has long been known, the synthesis of its isomers diisocyanogen (CN-NC) and isocyanogen (CNCN) has posed considerable difficulties. Only recently has the experimental formation of CN-NC been reported for the first time."] The precursor norbornadienone azine was flash-pyrolyzed and the ' 3C and 14N NMR spectra of the pyrolysis products were consistent with the presence of CNNC.['] More recen...

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On the doubly ionized states of ammonia

Cited by 65 publications

References 12 publications

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

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

Auger Electron Spectra of Molecules: The First Row Hydrides

Diisocyanogen or Isocyanogen?

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