References of "Leyh, Bernard"
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See detailThe Photoionization of Vinyl Bromide Clusters.
Hoxha, A.; Locht, Robert ULg; Leyh, Bernard ULg et al

Book published by Berliner Elektronen Speicherring für Synchrotron Sthrahlung m.b.H (1999)

The optimization of the conditions for cluster production from C2H3Br is investigated. The dissociative photoionization of these species is reported, e.g. [C2H2Br]2+->C4H6Br++Br. An intracluster Penning ... [more ▼]

The optimization of the conditions for cluster production from C2H3Br is investigated. The dissociative photoionization of these species is reported, e.g. [C2H2Br]2+->C4H6Br++Br. An intracluster Penning ionization phenomenon is observed. [less ▲]

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See detailKinetic Energy Release Distributions in the Dissociation of Energy-Selected Fluoroethene and 1,1-Difluoroethene Ions.
Güthe, F.; Locht, Robert ULg; Leyh, Bernard ULg et al

in Journal of Physical Chemistry A (1999), 103

The unimolecular dissociation of energy-selected fluoroethene and 1,1-difluoroethene ions has been investigated by threshold photoelectron photoion coincidence TPEPICO) technique. The breakdown diagrams ... [more ▼]

The unimolecular dissociation of energy-selected fluoroethene and 1,1-difluoroethene ions has been investigated by threshold photoelectron photoion coincidence TPEPICO) technique. The breakdown diagrams of the 1,1-difluorethene and fluoroethene have been recorded between 13-22 eV. From time-of-flight (TOF) spectra, complete distributions of the kinetic energy released (KERD) in the dissociation of these energy-selected ions have been derived. For the HF-loss reaction channel, the KERD peaks at about 200 meV for low excitation energies but becomes thermal at higher excitation energies. For the F-loss channel, the KERD peaks at zero kinetic energy for low excitation energies but at about 200 meV for high excitation energy. The analysis of the KERD provides evidence that consecutive fragmentation takes place for the 1,1-difluoroethene at energies above 19 eV. [less ▲]

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See detailThree-dimensional Kinetic Energy Distributions of Ions using a Retarding Potential Analyser. Analysis of Discimination Effects by Ion Trajectory Simulations.
Hoxha, A.; Leyh, Bernard ULg; Locht, Robert ULg

in Rapid Communications in Mass Spectrometry : RCM (1999), 13

This paper presents a method of extracting three-dimensional kinetic energy distributions from retarding potential curves, suitable for analysing low kinetic energy releases. Trajectory calculations were ... [more ▼]

This paper presents a method of extracting three-dimensional kinetic energy distributions from retarding potential curves, suitable for analysing low kinetic energy releases. Trajectory calculations were performed which led to an analytical function correcting for the influence of discrimination against ions with velocity components perpendicular to the retarding field direction. The analysis of the thermal kinetic energy distribution of molecular vinyl bromide ions confirms the computed correcting factor. [less ▲]

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See detailShear-induced order in aqueous micellar solutions of amphiphilic poly(tert-butylstyrene)-b-poly(Na methacrylate) diblock
Leyh, Bernard ULg; Creutz, S.; Gaspard, J. P. et al

in Macromolecules (1998), 31(26), 9258-9264

Shear-induced order of aqueous micellar solutions of a poly(tert-butylstyrene)-b-poly(sodium methacrylate) diblock (c ) 2.5-15 w/v %) has been investigated by small-angle X-ray scattering. Data collected ... [more ▼]

Shear-induced order of aqueous micellar solutions of a poly(tert-butylstyrene)-b-poly(sodium methacrylate) diblock (c ) 2.5-15 w/v %) has been investigated by small-angle X-ray scattering. Data collected from a Couette cell in both radial and tangential geometries agree with a crystalline ordering of micelles in close packed hexagonal layers perpendicular to the velocity gradient, when c is in the 5-10 w/v % range. The measured interlayer distance is indeed very close to the value expected for a closepacked structure. The experimental data are consistent with a zigzag motion of adjacent planes upon shear. Shear-induced order is, however, restricted to a narrow concentration range just above the concentration for the sol-gel transition. This domain is thought to correspond to a regime where relative layer translation modes are allowed whereas mutual rotation is hindered. [less ▲]

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See detailReactivity of Halogenoethylene Ions using Photoionization and Collisional Activation.
Leyh, Bernard ULg; Hoxha, A.; Franck, B. et al

in Karjalainen, E. J.; Hesso, A. E.; Jalonen, J. E. (Eds.) et al Advances in Mass Spectrometry: Volume 14. (1998)

Unimolecular reactivity of ionized difluoroethylene and vinylbromide have been investigated using photoionization mass spectrometry and tandem mass spectrometry. Kinetic energy release distributions ... [more ▼]

Unimolecular reactivity of ionized difluoroethylene and vinylbromide have been investigated using photoionization mass spectrometry and tandem mass spectrometry. Kinetic energy release distributions corresponding to HF- and F- losses from 1,1-C2H2F2+ and to Br-loss from C2H3Br+ have been determined. At low internal energy the loss of HF from C2H2F2+ leads to the fluoroacetylene cation with a large kinetic energy release (0.4-2.5 eV) while at higher energy a new channel is opened, leading to C=CHF+ (fluorovinylidene) with a much smaller kinetic energy release (0.0-0.2 eV). For the F-loss from C2H2F2+ and the Br-loss from C2H3Br+ bimodal distributions have been observed. The possible role of excited states in these dissociations is discussed. [less ▲]

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See detailThe Photoionization of small Vinyl Bromide (C2H3Br)n Clusters.
Hoxha, A.; Leyh, Bernard ULg; Locht, Robert ULg et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1998)

The ionization and decomposition of small clusters produced from C2H3Br are investigated by threshold photoelectron-photoion coincidence spectroscopy.

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See detailThe threshold Photoelectron-Photoion Coincidence Spectroscopy of Vinyl Bromide (C2H3Br).
Hoxha, A.; Leyh, Bernard ULg; Locht, Robert ULg

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1998)

The dissociative ionization of C2H3Br has been investigated by threshold photoelectron-photoion coincidence spectroscopy using synchrotron radiation. The C2H3+, C2H2+, HBr+ and Br+ dissociation channels ... [more ▼]

The dissociative ionization of C2H3Br has been investigated by threshold photoelectron-photoion coincidence spectroscopy using synchrotron radiation. The C2H3+, C2H2+, HBr+ and Br+ dissociation channels were considered. [less ▲]

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See detailAbsorption and Ionization Spectroscopy of Methyl Halides and Deuterated Methyl halides between 6 and 12 eV.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1998)

The vacuum UV photoabsorption spectrum of CH3Cl and CD3Cl have been measured between 6 and 12 eV photon energy. The photoionization efficiency curve of CH3+ provided by dissociative photoionization of ... [more ▼]

The vacuum UV photoabsorption spectrum of CH3Cl and CD3Cl have been measured between 6 and 12 eV photon energy. The photoionization efficiency curve of CH3+ provided by dissociative photoionization of CH3Cl is reported. The attention is focussed on the ion-pair CH3+/Cl- formation. [less ▲]

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See detailA He(I) Photoelectron Spectroscopic Study of the X2A"2state of NH3+ and ND3+. A Reanalysis and evidence for the Coriolis Coupling between the Bending nu2 and nu4 Modes.
Locht, Robert ULg; Leyh, Bernard ULg; Hottmann, K. et al

in Chemical Physics (1998), 233

In the He(I) photoelectron spectrum of NH3 and its isotopomer ND3 the complete vibrational structure of the X2A"2 state of NH3+ and ND3+ is examined in detail. Three vibrational progressions are ... [more ▼]

In the He(I) photoelectron spectrum of NH3 and its isotopomer ND3 the complete vibrational structure of the X2A"2 state of NH3+ and ND3+ is examined in detail. Three vibrational progressions are identified. The well-known strongest progression, already unambiguously assigned to the nu2 out-of-plane bending mode, is observed from v=0-17 in NH3+ and v=0-20 in ND3+. For NH3+ this vibration could be characterized not only by its energy hcomega2= 0.109+/-0.001 eV (or omega2= 878+/-7 cm-1) but also by its first anharmonicity constant hcomega22x22=-(16.2+/-1.2)10-4 eV (or omega22x22=-13.0+/-1.0 cm-1). The best fit of the experimental data required the introduction of a second anharmonicity constant, i.e. hcomega22y22= -(30.7+/-4.2)x10-6 eV (or omega22y22=-0.248+/-0.034 cm-1). The earlier reported weak progression assigned to the vibrational combination nu1+nnu2 transitions has been reexamined. Suitable handling of the data leads to two possible energies for the nu1 degenerate NH stretching vibrational normal mode, i.e. hcomega1 =0.306+/-0.006 eV or 0.422+/-0.005 eV. Several arguments are brought to favour the value of hcomega1=0.422 eV (or omega1=3404 cm-1). Finally a third weak progression, reported for the first time, is assigned to nu4+nnu2 transitions where the nu4 in-plane bending mode is optically forbidden. This vibrational normal mode is characterized by an energy hcomega4=0.186+/-0.010 eV (omega4=1500+/-80 cm-1). In agreement with the theoretical predictions, this transition becomes allowed through a strong Coriolis vibro-rotational coupling between the nu4 and the nu2 vibrational normal modes. The same measurements and the isotope effect on the molecular constants are investigated in ND3+ too. [less ▲]

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See detailL'enseignement de la chimie aux étudiants du secondaire qui se destinent à l'université: Trois heures de chimie valent mieux qu'une
Cornélis, André ULg; Cahay, René ULg; Leyh, Bernard ULg

in Chimie Nouvelle (1998), 16

The major importance of a high quality chemistry education in secondary schools is highlighted by the analysis of the results of a procedure developed at the University of Liège to help the students ... [more ▼]

The major importance of a high quality chemistry education in secondary schools is highlighted by the analysis of the results of a procedure developed at the University of Liège to help the students starting their university education, to evaluate their level of basic chemistry competences and to improve them if necessary. It turns out that students who followed three weekly periods of chemistry per week in the secondary school are clearly favoured compared to those who had only one period. These discrepancies show up not only on the starting competence level but also on the progress realized during the remediation step. The starting competence level influences also the strategy chosen by the student for his/her individual remediation. [less ▲]

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See detailPhotoabsorption, He(I) and Threshold Photoelectron spectra and CIS-Spectroscopy of Vinylchloride.
Locht, Robert ULg; Leyh, Bernard ULg; Hottmann, K. et al

in Aumayr, F.; Betz, G.; Winter, H. P. (Eds.) XX. ICPEAC: Scientific Programme and Abstracts of Contributed Papers. Volume 1. (1997)

The Vacuum UV photoabsorption and Threshold Photoelectron spectra of C2H3Cl have been measured by using synchrotron radiation. Vibrationally resolved CIS-spectroscopy of the same molecule is also reported.

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See detailThe Photoionization of Methyl Iodide (CH3I). The Threshold Photoelectron and CIS Spectroscopy.
Locht, Robert ULg; Hoxha, A.; Leyh, Bernard ULg et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1997)

The vacuum UV photoabsorption spectrum of CH3I and its threshold photoelectron spectrum are reported. The region of 9.5-10.5 eV photon energy is recorded at high resolution.

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See detailThe Photoionization of Ethylene Monobromide (C2H3Br). The Threshold Photoelectron and CIS Spectroscopy.
Hoxha, A.; Locht, Robert ULg; Leyh, Bernard ULg et al

Book published by Berliner Elektronen Speicherring für Elektronen Synchrotron Strahlung m.b.H (1997)

The first results on the threshold photoelectron, CIS-spectroscopy and photoabsorption spectroscopy of C2H3Br are reported. A first analysis is presented.

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See detailThe He(I), Threshold photoelectron and Constant Ion State spectroscopy of Vinylchloride (C2H3Cl).
Locht, Robert ULg; Leyh, Bernard ULg; Hottmann, K. et al

in Chemical Physics (1997), 220

Using synchrotron radiation the threshold photoelectron (TPES) spectrum and constant ion state (CIS) spectroscopy of C2H3Cl are reported. For comparison, the He(I) photoelectron spectrum has also been ... [more ▼]

Using synchrotron radiation the threshold photoelectron (TPES) spectrum and constant ion state (CIS) spectroscopy of C2H3Cl are reported. For comparison, the He(I) photoelectron spectrum has also been measured and reexamined. The threshold photoelectron spectrum has been measured between 9.0 and 25.0 eV and the photon energy range of 9.9-12.0 eV has been investigated in detail. Many features have been identified and tentatively assigned with the help of the photoabsorption spectroscopic results. These data were compared with the well-resolved He(I) photoelectron spectrum. The fine structure observed in the two first ionic states is assigned to progressions belonging partially to previously unobserved vibration normal modes. State-selected CIS spectra have been recorded for the first vibronic states between 10.0 and 11.67 eV. They exhibit fine structure assigned to autoionization of Rydberg states. [less ▲]

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See detailThe Photoabsorption Spectrum of Vinylchloride (C2H3Cl) in the 8-12 eV Range.
Locht, Robert ULg; Leyh, Bernard ULg; Hottmann, K. et al

in Chemical Physics (1997), 220

The photoabsorption spectrum of vinylchloride (C2H3Cl) has been measured using synchrotron radiation and has been analyzed in detail between 8-12 eV photon energy. Valence and virtual valence and Rydberg ... [more ▼]

The photoabsorption spectrum of vinylchloride (C2H3Cl) has been measured using synchrotron radiation and has been analyzed in detail between 8-12 eV photon energy. Valence and virtual valence and Rydberg transitions have been identified and classified. Tentative assignments were based on the ionization energies as measured by He(I)- and threshold photoelectron spectroscopy, as reported in the joined paper. Many features have been identified as being members of vibrational progressions belonging to the observed Rydberg series. [less ▲]

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See detailPhotoabsorption and Photoionization of Mono- and Difluoroethylenes.
Leyh, Bernard ULg; Locht, Robert ULg; Hottmann, K. et al

in Aumayr, F.; Betz, G.; Winter, H. P. (Eds.) XX. ICPEAC: Scientific Programme and Abstracts of Contributed Papers. (1997)

The Vacuum UV photoabsorption spectrum and the threshold photoelectron spectrum of C2H3F and 1,1-C2H2F2 have been measured by using synchrotron radiation. CIS-spectra have been recorded for several ... [more ▼]

The Vacuum UV photoabsorption spectrum and the threshold photoelectron spectrum of C2H3F and 1,1-C2H2F2 have been measured by using synchrotron radiation. CIS-spectra have been recorded for several electronic states of both molecules. [less ▲]

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See detailMechanism of Single-Electron Capture by the Dichlorocarbene Dication.
Leyh, Bernard ULg; Hautot, D.

in Journal of the American Society for Mass Spectrometry (1996), 7

The single-electron capture (SEC) by dichlorocarbene with eight different atomic and molecular target gases, (CCl2)2++G->(CCl2)++G+, has been studied by product ion spectroscopy and ion kinetic energy ... [more ▼]

The single-electron capture (SEC) by dichlorocarbene with eight different atomic and molecular target gases, (CCl2)2++G->(CCl2)++G+, has been studied by product ion spectroscopy and ion kinetic energy spectroscopy. The experimental data have been interpreted in the framework of a theoretical model that describes the charge exchange process. Exothermic charge exchange is handled within the Landau-Zener model, whereas endothermic charge exchange is described by the Demkov model. The calculated data reproduce qualitatively the essential features of the experimental results: (1) the appearance of a reaction window centered at an exothermicity in the 4-4.5 eV range, (2) the lower SEC cross sections for endothermic charge exchange, (3) the wider internal energy distributions obtained for CCl2+ in the endothermic regime than in the exothermic one, which results in larger dissociation yields, (4) the excitation of molecular targets that accompany their ionization in the SEC process, and (5) the kinetic energy released on the CCl++Cl fragments in dissociative SEC. [less ▲]

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See detailUnimolecular Reaction Dynamics from Kinetic Energy Release Distributions. 2. A Study of the Reaction C6H5Br+->C6H5++Br by the Maximum Entropy Method.
Urbain, P.; Remacle, Françoise ULg; Leyh, Bernard ULg et al

in Journal of Physical Chemistry (1996), 100(19), 8003-8007

The kinetic translational energy released in the unimolecular fragmentation reaction C6H5Br+->C6H5++Br has been experimentally studied in the microsecond time scale and theoretically analyzed by the ... [more ▼]

The kinetic translational energy released in the unimolecular fragmentation reaction C6H5Br+->C6H5++Br has been experimentally studied in the microsecond time scale and theoretically analyzed by the maximum entropy formalism. The appropriate functional form relating the actual distribution to its prior distribution (eq.2.3) involves the square root of the kinetic energy (i.e. the momentum associated with the relative translational energy). A value of 0.26+/-0.02 eV is obtained by the entropy deficiency distribution at an internal energy of 0.85 eV above the reaction threshold. From this value, it can be concluded that 77% of the transition state phase space is efficiently sampled. [less ▲]

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See detailThe Threshold Photoelectron, CIS- and Photoabsorption Spectra of the Methyl Monohalides (Cl, Br, and I).
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1996)

The threshold photoelectron, the CIS and the vacuum UV photoabsorption spectra of the Methyl halides CH3X (X=Cl,Br and I) were measured by using synchrotron radiation. Several physical magnitudes are ... [more ▼]

The threshold photoelectron, the CIS and the vacuum UV photoabsorption spectra of the Methyl halides CH3X (X=Cl,Br and I) were measured by using synchrotron radiation. Several physical magnitudes are reported. [less ▲]

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See detailThe Threshold Photoelectron and Constant Ion State Spectra of the three Dichloroetylene Isomers.
Leyh, Bernard ULg; Locht, Robert ULg; Hottmann, K. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1996)

Using synchrotron radiation, the threshold phototelectron spectrum and the Constant Ion State (CIS) spectrum of the three isomers of dichloroethylene are reported. Adiabatic ionization energies and ... [more ▼]

Using synchrotron radiation, the threshold phototelectron spectrum and the Constant Ion State (CIS) spectrum of the three isomers of dichloroethylene are reported. Adiabatic ionization energies and vibrational wavenumbers are measured. [less ▲]

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