Unimolecular decay measurements of secondary ions from organic molecules by time-of-flight mass spectrometry

Schueler, B.; Beavis, Ronald C.; Ens, Werner; Main, D. E.; Tang, Xuejun; Standing, Kenneth G.

doi:10.1016/0168-1176(89)83027-7

Cited by 15 publications

(6 citation statements)

References 16 publications

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“…Even with some fluctuation in the ion current, which is inherent in the FAB technique, the reproducibility of the measured rates varies by less than 20%. This rate is indeed smaller than the rates of FAB-produced phenylalanine ions reported by Schueler et aL [4].…”

Section: Resultscontrasting

confidence: 52%

“…A study by Schueler et a1. [4] to determine the effects of varying the primary beam energy from 3 to 13 keY on the unimolecular rate constants shows no dependence between the two. Similar experiments were attempted with FTMS, but the overall signal-to-noise ratio varied greatly with the primary beam energy.…”

Section: Resultsmentioning

confidence: 96%

“…Unimolecular rate constants as low as 2.3 X 10 3 S-1 are reported by Schueler et a1. [4] with para-substituted phenylalanine ions produced by liquid secondary ion mass spectrometry or, more conveniently, FAB, and observed with a time-offlight mass.spectrometer [4].…”

mentioning

confidence: 99%

“…To observe unimolecular decay of ions produced in the FTMS instrument, it must be at least an order of magnitude less than those reported by Schueler et a1. [4]. Recently, Guan and McIver [27] reported slow metastable decay of larger FAB-produced peptides in an external source FTMS instrument; however, actual unimolecular decomposition rate constants were not obtained.…”

mentioning

confidence: 99%

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“Slow” metastable decomposition of oligosaccharide cations produced in an external source fourier transform mass spectrometer

Ngoka

Lebrilla

1993

J. Am. Soc. Mass Spectrom.

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Section: Resultscontrasting

confidence: 52%

Section: Resultsmentioning

confidence: 96%

mentioning

confidence: 99%

mentioning

confidence: 99%

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“Slow” metastable decomposition of oligosaccharide cations produced in an external source fourier transform mass spectrometer

Ngoka

Lebrilla

1993

J. Am. Soc. Mass Spectrom.

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“…The “negative” voltage part (with respect to the reference corresponding to the 2 kV acceleration voltage) of the axial energy distributions provides us with information about ions that do not have the full acceleration energy. Since ionization far from the surface should be negligible, it can be assumed that these ions are produced by metastable decay of larger parent ions in the acceleration section or the field-free drift region of the spectrometer. ,− Polyatomic secondary ions that loose a neutral atom or molecule in those regions also loose a fraction of kinetic energy proportional to the mass of the neutral loss, thereby appearing as a signal corresponding to a negative voltage or energy in our measurements. As an example, a monomer ion of Irganox with a 4 eV energy deficit, resulting from the decay of a charged dimer, would correspond to a dissociation reaction occurring ∼6 μm above the surface in our instrument (2 kV over ∼1.5 mm).…”

Section: Results and Discussionmentioning

confidence: 99%

Mechanistic Insight into Gas Cluster-Induced Sputtering of Kilodalton Molecules Using Kinetic Energy Distribution Measurements

Delcorte

Poleunis

2019

J. Phys. Chem. C

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Recent progress in organic secondary ion mass spectrometry (SIMS) relied essentially on the development of new cluster beams, especially large atomic and molecular clusters formed via the adiabatic expansion of a gas in vacuum (Ar n +, [CH4] n +, [CO2] n +, [H2O] n +). Although computer simulations and a few experimental investigations have shed light on certain fundamental aspects of large cluster-induced molecular desorption, the analytical application of these new beams usually preceded the detailed understanding of their interaction with surfaces. Here, to gain insight into the molecular emission process, the axial kinetic energy distributions (KEDs) of secondary ions emitted from organic films bombarded with Ar330–5000 + and Bi5 + clusters were measured using a reflectron time-of-flight secondary ion mass spectrometer. Irganox 1010 was chosen as a model kilodalton molecule because a large body of SIMS data involving this molecule already exists in the literature. Our results show that the axial KED of Irganox molecular and fragment ions varies as a function of the scaled kinetic energy E/n of the Ar cluster projectile and so does the fraction of ions produced above the surface via unimolecular dissociation, which exhibit an energy deficit with respect to the full acceleration provided at the entrance of the spectrometer. Below a few tens of eV/atom, the KEDs of ions such as (M – H)− (m/z 1175) become gradually narrower and their formation via metastable decay in the gas phase above the surface intensifies. Interestingly, the molecular ion M•+ (m/z 1176) is essentially produced in the gas phase with both Ar n + and Bi5 + cluster beams. Specifics of the observed KEDs of negative and positive molecular ions are discussed in comparison with results of other experiments recently reported in the literature and of molecular dynamics (MD) computer simulations using a coarse-grained representation of kilodalton organic molecules. The measurement of the axial kinetic energy of molecular and fragment ions sputtered from Irganox 1010 under argon and bismuth cluster bombardment, complemented with MD simulations, offers a clearer microscopic view of the emission process.

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Comparative investigations of the secondary ion emission of metal complexes under MeV and keV ion bombardment

Feld¹,

Rading²,

Leute³

et al. 1993

Org. Mass Spectrom.

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A series of ionic and neutral Group VIII transition metal complexes with molecular masses up to 2500 u were analysed by time-of-flight secondary ion mass spectrometry (SIMS) and plasma desorption mass spectrometry (PDMS). The secondary ion emission, the secondary ion yields and the yield ratios Y(PDMS)/Y(SIMS) of 20 ionic and neutral metal complexes were determined. Both techniques generally provide both molecular and fragment ion information. Characteristic fragmentation patterns give useful data for structural cbaracterization. Additionally, the stabilities of different secondary ion species were compared by their half-lives. Both PDMS and SIMS are very sensitive, yielding optimum spectra from total sample sizes as low as 5 nmol, and the sample consumption is negligible.( 1 ) D btai ;kh;ol e (chelat) = L, (N03-)2 Me = Pd, P t Figure 1 . General scheme of the investigated dicationic metal complexes (after Ref. 8).

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Unimolecular decay measurements of secondary ions from organic molecules by time-of-flight mass spectrometry

Cited by 15 publications

References 16 publications

“Slow” metastable decomposition of oligosaccharide cations produced in an external source fourier transform mass spectrometer

“Slow” metastable decomposition of oligosaccharide cations produced in an external source fourier transform mass spectrometer

Mechanistic Insight into Gas Cluster-Induced Sputtering of Kilodalton Molecules Using Kinetic Energy Distribution Measurements

Comparative investigations of the secondary ion emission of metal complexes under MeV and keV ion bombardment

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