Matrix effects, internal energies and MS/MS spectra of molecular ions sputtered from surfaces

Cooks, R. Graham; Busch, Kenneth L.

doi:10.1016/0020-7381(83)85106-7

Cited by 149 publications

(76 citation statements)

References 35 publications

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“…In 1983, Cooks and Busch [3] noted a systematic increase in the abundance ratio of precursor ion to product ions with decreasing analyte concentration during secondary ion mass spectrometric analyses of organic compounds in an ammonium chloride matrix. The effect was attributed to the cooling effect of dissociation of [analyte ion/matrix neutral] complexes following the initial desorption step.…”

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confidence: 99%

“…It is known that during the MALDI process clusters of matrix and analyte species are ablated into the gas phase [3,[5][6][7][8][9][10]. These clusters are held together by hydrogen bonding and coulombic interactions [5] and the post-desorption loss of matrix neutrals from the clusters has been postulated to reduce the internal energies of the analyte ions released [3,5,10]. These suggestions have been substantiated by molecular dynamics calculations of the internal energies of analyte ions in laser-desorbed clusters, showing a decrease associated with progressive evaporation of matrix molecules [10].…”

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Comparison of the effects of ionization mechanism, analyte concentration, and ion “cool-times” on the internal energies of peptide ions produced by electrospray and atmospheric pressure matrix-assisted laser desorption ionization

Konn

Murrell

Despeyroux

et al. 2005

J. Am. Soc. Mass Spectrom.

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The propensities of a series of peptide ions produced by both electrospray and atmospheric pressure matrix assisted laser desorption ionization (AP-MALDI) to fragment in an ion trap mass spectrometer under various conditions were studied in detail by measuring the extent of fragmentation of precursor ions by collision induced dissociation (CID) as a function of applied resonance excitation RF voltage. For the most basic peptides, the energy required to fragment MH ϩ ions generated by electrospray exceeded that required to fragment equivalent AP-MALDI ions under identical instrumental conditions; the reverse was observed for a peptide incorporating no basic residues, while peptides of intermediate basicity showed little difference between the ionization methods. This correlation between peptide basicity and the difference in the energy required to induce fragmentation of MH ϩ ions generated by AP-MALDI and electrospray is attributed primarily to a trend in the internal energies of the ions generated by AP-MALDI (the greater the difference in gas-phase basicities between the matrix and the analyte the greater the internal energy of the analyte ions produced). Furthermore the internal energies of ions produced by AP-MALDI, but not the equivalent ions formed by electrospray, were observed to decrease with decreasing analyte concentration. We attribute this finding to the cooling effect of endothermic dissociation of analyte ion/matrix molecule clusters following the matrix assisted laser desorption step. Time-resolved analyses (measurement of extent of fragmentation of precursor ions by CID as a function of pre-CID "cool times") revealed that cooling periods in excess of 250 ms were required to achieve internal energy equilibrium through cooling collisions with the helium buffer gas. Furthermore, these analyses demonstrated that, even after these extended cooling times, equivalent ions formed by the two ionization techniques showed different propensities to fragment. We conclude that the two different ionization techniques produce ion populations that may differ in their three-dimensional structure. T he initial internal energy of an ion is determined by the internal energy of the analyte molecule before ionization and the energy deposited during ionization. The additional internal energy that must be acquired during ion activation in order for dissociation to occur is defined by the initial internal energy of the ion. Thus, for a fixed activation energy the extent of ion decomposition is a measure of the initial internal energy of that ion. Therefore, in order to compare the initial internal energies of peptide ions produced by electrospray and AP-MALDI, a series of energyresolved tandem mass spectrometry experiments were performed, in which the extent of decomposition of precursor ions by CID was measured as a function of applied resonance excitation RF voltage.Danell and Glish [1] and Wysocki and coworkers [2] investigated the differences between the internal ener-

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mentioning

confidence: 99%

Comparison of the effects of ionization mechanism, analyte concentration, and ion “cool-times” on the internal energies of peptide ions produced by electrospray and atmospheric pressure matrix-assisted laser desorption ionization

Konn

Murrell

Despeyroux

et al. 2005

J. Am. Soc. Mass Spectrom.

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“…Several investigators [16][17][18] already described the model of desorption-ionization (DI) processes for organic molecules in mass spectrometry, and the detailed example and discussion was indicated by Lenaerts and co-workers: 19 Fast thermal processes are assumed to be responsible for generating primarily neutrals in the selvedge. Electrons and protons that are also present in the selvedge give rise to, respectively, electron ionization (EI) and adduct ionization (AI) of these neutrals.…”

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Simulation of SIMS for monomer and dimer of lignin under the assumption of thermal decomposition using QMD method

Kato

Endo

Matsumoto

et al. 2008

Applied Surface Science

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The thermal decomposition of the monomer and dimer of lignin has been simulated by a quantum molecular dynamics (DMD) method. In the calculation, we controlled the total energy of the system using Nóse-Hoover thermostats in the total energy range of 0.69 ~ 0.95 eV, and the sampling position data with a time step of 0.5 fs were carried out up to 3000 (1.5 ps) or 5000 (2.5 ps) steps in ab initio and semiempirical MO methods, respectively. We obtained the thermally decomposed fragments with positive, neutral and negative charges from SCF MO calculation at each data of the last MD step, and simulated the fragment distribution of the monomer and dimer lignins from the last step in 30 ~ 40 runs. Simulated mass numbers of positively and negatively charged fragments for lignin monomer and dimer showed considerably good accordance with the experimental results in TOF-SIMS observed by Saito and co-workers.

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“…In the DI model [45,46], desorption (or ablation) and ionization occur successively after photon bombardment in different regions of the selvedge. Molecular and pseudomolecular species as ion pairs or neutrals are first emitted from the solid according to fast thermal or sputtering processes.…”

Section: Study Of Cluster Ion Formation By La-msmentioning

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Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Aubriet

Müller

2008

J. Am. Soc. Mass Spectrom.

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Laser ablation of transition-metal oxides have been investigated to better understand the formation processes of inorganic cluster ions. The study of binary oxide mixtures and the relative distribution of the ions produced suggest three salient mechanisms that occur after laser/matter interaction, that function to produce the observed ensemble of ionic species. Molecular recombination reactions, unimolecular dissociation processes, emission of small neutrals, including molecular oxygen from transition-metal oxide samples, or from species expelled in gas phase appear to be a significant mechanism, especially under high laser irradiance conditions. These processes are used to propose a set of pathways to rationalize the envelope of ionic clusters formed under photon bombardment. T he study of ion formation processes by mass spectrometry during inorganic compound laser ablation is not yet fully understood. However, several models have been proposed to describe and explain the laser ablation of inorganic compounds [1][2][3][4][5][6][7]. The interaction of a laser beam with a non-metallic solid induces different processes, leading to ejection of neutral and ionized species into the gas phase. Haglund proposed a qualitative description of these processes [7], which begins with the assumption that laser sputtering could be decomposed into four phases: (1) the absorption of laser energy by one or multiple-photon processes; (2) the conversion of the incident energy through radiative and non-radiative relaxation processes; (3) the ejection of species-atoms, molecules, neutrals, ions, excited species-from the irradiated surface; and (4) the formation and the expansion of a more or less dense plume of neutrals and ions. Two lasermatter interaction regimes have to be considered: the laser desorption (LD) and the laser ablation (LA). It is generally reported that LD results in emission of ions, atoms, and molecules without any substantial disturbance in the surrounding surface. LA implies a largescale disruption of surface and near-surface geometrical and electronic structure. These substantial qualitative differences allowed Haglung to identify desorption with a microscopic, and ablation with a mesoscopic view point. LD and LA have to be viewed as the extremes of a continuum, which ranges from the emission of isolated neutrals or ions in the case of LD to the massive removal of material resulting from the collective effects of multiple photons irradiating the same spatial locale in the case of LA. The phenomenology of LA is thought of in terms of formation of a plume of ejected species, which follows the laws of plasma and gas dynamics, and produces a large number of ionized species. Collisions of ions with neutrals occurring in the gas-phase plume after LA lead to ion-molecule condensation reactions. On the other hand, ions and neutrals possess a significant amount of energy, which can result in dissociation reactions. The length scale associated with laser ablation is on the order of d Х laser ϫv s , where laser is the dur...

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Matrix effects, internal energies and MS/MS spectra of molecular ions sputtered from surfaces

Cited by 149 publications

References 35 publications

Comparison of the effects of ionization mechanism, analyte concentration, and ion “cool-times” on the internal energies of peptide ions produced by electrospray and atmospheric pressure matrix-assisted laser desorption ionization

Comparison of the effects of ionization mechanism, analyte concentration, and ion “cool-times” on the internal energies of peptide ions produced by electrospray and atmospheric pressure matrix-assisted laser desorption ionization

Simulation of SIMS for monomer and dimer of lignin under the assumption of thermal decomposition using QMD method

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

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