Influence of the photoionization process on the fragmentation of laser desorbed polycyclic aromatic hydrocarbons

Thomson, Kevin A.; Ziskind, Michaël; Mihesan, C.; Therssen, E.; Desgroux, Pascale; Focşa, Cristian

doi:10.1016/j.apsusc.2007.01.050

Cited by 18 publications

(20 citation statements)

References 23 publications

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“…Figure 1 shows the radial profiles of f v and LIF taken at different reaction times (e.g., different heights above the burner (HAB)) in the four turbulent flames. The profiles behaviour with HAB is quite similar to that observed in laminar diffusion sooting flames [17,22] except in the case of n-decane which is almost non-sooting. As shown later, the LIF profile behaviour is consistent with the contribution of soot precursors and presumably high-number-ring PAHs.…”

Section: Global Description and Comparison Of The Flames Structuresupporting

confidence: 72%

“…Secondly, the ionisation probe volume has been greatly increased introducing a non-focused laser beam in the ionisation chamber. The selection of the laser beam shape originates from [22] but the cylindrical focusinglens has been replaced here by a relay-imaging set-up in which a 0.5 Â 10 mm slit is imaged via a two-lens system at the centre of the desorbed plume. This configuration increases the number of ionised molecules permitting lower ionisation fluence and consequently fragment-free analyses, a better mass resolution and an enhanced sensitivity.…”

Section: Laser-desorption Ionisation Time-of-flight Mass Spectrometrymentioning

confidence: 99%

“…In comparison with mass spectra from soot particles sampled at the exhaust of Diesel engines, the sampling within our Diesel (or surrogate) flames highlights lighter PAHs. It must be emphasised that our set-up allows volatile compounds to be analysed thanks to nitrogen cooling of the soot sample during the LDI TOF-MS procedure [17,22].…”

Section: Analysis Of the Species Adsorbed On Soot Surfacementioning

confidence: 99%

“…A detailed description has been reported elsewhere [17,22]. Briefly, the sample surface is irradiated at normal incidence by the beam of a 7 ns doubled Nd:YAG laser (k = 532 nm) to promote thermal desorption of neutral species.…”

Section: Laser-desorption Ionisation Time-of-flight Mass Spectrometrymentioning

confidence: 99%

See 3 more Smart Citations

Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels

Lemaire

Faccinetto

Therssen

et al. 2009

Proceedings of the Combustion Institute

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103

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Section: Global Description and Comparison Of The Flames Structuresupporting

confidence: 72%

Section: Laser-desorption Ionisation Time-of-flight Mass Spectrometrymentioning

confidence: 99%

Section: Analysis Of the Species Adsorbed On Soot Surfacementioning

confidence: 99%

Section: Laser-desorption Ionisation Time-of-flight Mass Spectrometrymentioning

confidence: 99%

See 2 more Smart Citations

Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels

Lemaire

Faccinetto

Therssen

et al. 2009

Proceedings of the Combustion Institute

Self Cite

103

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“…Neutral species in the desorption plume are then ionized by an orthogonal delayed UV light source. The used UV light source is either a Nd:YAG laser beam (Continuum Powerlite 8010, 6 ns, 266 nm, 10 Hz) for the Resonant Two-Photon Ionization (R2PI) of most of the aromatic species (Thomson et al, 2007;Mihesan et al, 2008), or a 118 nm (10.5 eV) focused beam of a coherent source generated by four-wave mixing in a Xe-cell (Butcher et al, 1999) and enabling Single Photon Ionization (SPI) of most of the condensable species including aliphatic compounds (Desgroux et al, 2013). Both desorption and ionization laser intensities are kept close to the threshold (typically several MW cm -2 ) to avoid fragmentation of analytes.…”

Section: Methodsmentioning

confidence: 99%

Chemical Composition of Diesel/Biodiesel Particulate Exhaust by FTIR Spectroscopy and Mass Spectrometry: Impact of Fuel and Driving Cycle

Popovicheva

Irimiea

Carpentier

et al. 2017

Aerosol Air Qual. Res.

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The growing concern about air quality and the impact exhaust particles can have on the environment has resulted in the increased use of alternative fuels. A sampling campaign from a conventional heavy diesel engine operated in typical transient cycle or steady-state condition, and running on diesel, 30% biodiesel in diesel, and 100% biodiesel was carried out. The particulate composition was characterized using Fourier Transform Infrared (FTIR) spectroscopy, Two-step Laser Mass Spectrometry (L2MS), Secondary Ion Mass Spectrometry (SIMS), thermo-optical analysis, and capillary electrophoresis. Elemental carbon is demonstrated to decrease from diesel to 100% biodiesel, in agreement with the evolution of aromatic bands and the MS abundance of C n -fragments, while organic carbon exhibits a constant level irrespective of the working regime. Aliphatic, aromatic, carboxyl, carbonyl, hydroxyl functionalities, and nitro compounds are found to depend on the engine-working regime. Mass spectra are mainly characterized by alkyl fragments (C n H 2n+1 + ), associated to normal and branched alkanes, PAHs and their alkylated derivatives. The addition of biodiesel to diesel changes the particulate composition towards more oxygenated constituents, such as carbonyl groups attributed to methyl ester CH 3 O + fragments of unburned biodiesel. Fuel-specific fragments have been identified, such as C 3 H 7 O + for diesel, and C 2 H 3 O 2 + and CH 3 O -for biodiesel. Nitrogenized compounds are revealed by -NO 2 functionalities and N-containing fragments. Principal Component Analysis (PCA) was successfully applied to discriminate the engine operating conditions, with a higher variance given by the fuel, thus allowing to better evaluate the environmental impacts of alternative energy source emissions.

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Ultraviolet laser desorption/ionization mass spectrometry of single-core and multi-core polyaromatic hydrocarbons under variable conditions of collisional cooling: insights into the generation of molecular ions, fragments and oligomers

et al. 2014

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The ultraviolet laser desorption/ionization of polyaromatic hydrocarbons (PAHs) has been investigated under different background pressures of an inert gas (up to 1.2 mbar of N2) in the ion source of a hybrid, orthogonal-extracting time-of-flight mass spectrometer (oTOF-MS). The study includes an ensemble of six model PAHs with isolated single polyaromatic cores and four ones with multiple cross-linked aromatic and polyaromatic cores. In combination with a weak ion extraction field, the variation of the buffer gas pressure allowed to control the degree of collisional cooling of the desorbed PAHs and, thus, to modulate their decomposition into fragments. The dominant fragmentation channels observed are related to dehydrogenation of the PAHs, in most cases through the cleavage of even numbers of C-H bonds. Breakage of C-C bonds leading to the fragmentation of rings, side chains and core linkages is also observed, in particular, at low buffer gas pressures. The precise patterns of the combined fragmentation processes vary significantly between the PAHs. The highest abundances of molecular PAH ions and cleanest mass spectra were consistently obtained at the highest buffer gas pressure of 1.2 mbar. The effective quenching of the fragmentation pathways at this elevated pressure improves the sensitivity and data interpretation for analytical applications, although the fragmentation of side chains and of bonds between (poly)aromatic cores is not completely suppressed in all cases. Moreover, these results suggest that the detected fragments are generated through thermal equilibrium processes rather than as a result of rapid photolysis. This assumption is further corroborated by a laser desorption/ionization post-source decay analysis using an axial time-of-flight MS. In line with these findings, covalent oligomers of the PAHs, which are presumably formed by association of two or more dehydrogenated fragments, are detected with higher abundances at the lower buffer gas pressures.

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Influence of the photoionization process on the fragmentation of laser desorbed polycyclic aromatic hydrocarbons

Cited by 18 publications

References 23 publications

Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels

Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels

Chemical Composition of Diesel/Biodiesel Particulate Exhaust by FTIR Spectroscopy and Mass Spectrometry: Impact of Fuel and Driving Cycle

Ultraviolet laser desorption/ionization mass spectrometry of single-core and multi-core polyaromatic hydrocarbons under variable conditions of collisional cooling: insights into the generation of molecular ions, fragments and oligomers

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