References of "Leyh, Bernard"
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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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See detailThe Vacuum UV Photoabsorption Spectra of the three Dichloroethylene Isomers.
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 vacuum UV photoabsorption spectra of the three isomers of dichloroethylene, as measured with synchrotron radiation, are reported.

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See detailThe elementary reactions of energy selected 1,1-Difluoroethene ions.
Güthe, F.; Weitzel, K.-M.; Baumgärtel, H. et al

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

The dissociative photoionization dynamics of 1,1-difluoroethene has been investigated by TPEPICO using synchrotron radiation. The breakdown diagram has been build. The attention has been focussed on C2HF ... [more ▼]

The dissociative photoionization dynamics of 1,1-difluoroethene has been investigated by TPEPICO using synchrotron radiation. The breakdown diagram has been build. The attention has been focussed on C2HF+ (HF-loss) channel. [less ▲]

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See detailReactivity and Collisionally Activated Dichlorocarbene Dications studied by Tandem Mass Spectrometry.
Leyh, Bernard ULg; Hautot, D.

in Journal of the American Society for Mass Spectrometry (1995), 6

The dissociation mechanisms of dichlorocarbene dications following collisional activation have been investigated via tandem mass spectrometric technique and semi-empirical calculations. Three channels ... [more ▼]

The dissociation mechanisms of dichlorocarbene dications following collisional activation have been investigated via tandem mass spectrometric technique and semi-empirical calculations. Three channels appear to be significant: (CCl2)2+->CCl+(X1Sigma+)+Cl+(3P) (channel 1); (CCl2)2+->CCl+(X1Sigma+)+Cl+(1D) (channel 2); (CCl2)2+->(Cl2)+(X2Pig)+C+(2P). The second channel becomes dominant at high internal energy. Production of ground state fragments (channel 1) involves a transition driven by spin-orbit coupling from the (CCl2)2+ X 1Sigma+g state to the (CCl2)2+ a 3Sigma-u state en route to the fragments. The dissociation barrier for the production of the ground state fragments from the ground electronic state of (CCl2)2+ via the spin-orbit-induced transition is equal to 420 kJ/mol. The dissociation pathway that corresponds to channel 3 includes a first isomerization step from the linear (Cl-C-Cl)2+ structure to a bent (Cl-C-Cl)2+ connectivity. The calculated isomerization barrier amounts to 550 kJ/mol. The calculated reverse activation barriers are compatible with the measured kinetic energy released on the fragments. [less ▲]

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See detailReaction Window in the single-electron capture by Ammonia Dications.
Leyh, Bernard ULg; Hoxha, Antuan

in Chemical Physics (1995), 192

Single-electron capture (SEC) by (NH3)2+ with rare gases (He, Ne, Ar, Kr, Xe) and benzene, (NH3)2++G->NH3++G+, has been investigated using a forward geometry double-focussing mass spectrometer. The SEC ... [more ▼]

Single-electron capture (SEC) by (NH3)2+ with rare gases (He, Ne, Ar, Kr, Xe) and benzene, (NH3)2++G->NH3++G+, has been investigated using a forward geometry double-focussing mass spectrometer. The SEC cross-section goes through a maximum within a reaction window centered at an exothermicity of approximately 4.5 eV. This corresponds to a target-projectile distance for the charge transfer of about 3.2 Angstöm. The average internal energy of NH3+-ions resulting from SEC has been obtained both via translational energy gain measurements and via an analysis of the daughter ion spectra. The agreement between both methods is satisfactory and shows that the lower the ionisation energy of the target, the more probable the excitation of NH3+ to the A2E state. With benzene (ionization energy=9.25 eV) as the target gas, however, the excess energy is converted partly to internal energy of C6H6+, leading most probably to the D2B2u, E2B1u and F2A1g states of C6H6+. A model based on the Landau-Zener non-adiabatic formalism, including one entrance channel (NH32++G) and two exit channels (NH3+ X2A"2+G+ and NH3+ A2E+G+) accounts qualitatively for the observed results in the case of exothermic single-electron capture. This model is not appropriate for slightly exothermic and endothermic charge transfer, i.e., in the present case, for the Ne and He target gases. [less ▲]

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

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1995)

Using synchrotron radiation, the threshold photoelectron spectrum and vibrationally resolved CIS-spectra have been recorded between 10-28 eV photon energy for C2H3F and 1,1-C2H2F2.

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See detailResonant Autoionization in Vinylchloride between 10-12 eV.
Locht, Robert ULg; Leyh, Bernard ULg; Hottmann, K. et al

Book published by Berliner Elektronen Speischerring für Synchrotron Strahlung m.b.H (1995)

The threshold photoelectron spectrum of Vinylchloride has been recorded using synchrotron radiation. The attention is focussed on the abundant fine structure between 10-12 eV and has been assigned to ... [more ▼]

The threshold photoelectron spectrum of Vinylchloride has been recorded using synchrotron radiation. The attention is focussed on the abundant fine structure between 10-12 eV and has been assigned to vibrational autoinization. [less ▲]

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See detailChemical Reactions in the Cluster Ions of 1,1-Difluoroethene and Argon.
Güthe, F.; Jochims, H.-W.; Leyh, Bernard ULg et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1995)

The preparation conditions of 1,1-difluoroethene-Ar clusters has been investigated by photoionization using synchrotron radiation. The nature of the products has been identified by a quadrupole mass ... [more ▼]

The preparation conditions of 1,1-difluoroethene-Ar clusters has been investigated by photoionization using synchrotron radiation. The nature of the products has been identified by a quadrupole mass spectrometer. [less ▲]

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See detailReaction Dynamics of Collisionally activated Ammonia Cations.
Leyh, Bernard ULg; Hoxha, A.

in Chemical Physics (1994), 179

In the framework of a research on the collisional mechanisms involved in tandem mass spectrometry, the collisional activation processes of NH3+ with different target gases have been investigated. The ... [more ▼]

In the framework of a research on the collisional mechanisms involved in tandem mass spectrometry, the collisional activation processes of NH3+ with different target gases have been investigated. The experiments have been performed on an upgraded AEI-MS9 sector instrument equipped with two collision cells and include daughter ion spectra, ion kinetic energy spectra, determination of kinetic energy release distributions (KERD) and appearance energy measurements. We have shown that collisionally activated dissociation (CAD) of NH3+ into NH++[H,H] depends upon the internal energy of NH3+. This internal energy effect is also observed for the NH2++H channel, when Xe is the target gas; with He, such an effect could not be detected. The analysis of the KERD shows that production of NH2+ upon CAD takes place from the NH3+ ground electronic state by rotational predissociation; two components are observed, one which corresponds to a near-threshold process (mean kinetic energy release <T>=0.13 eV), and one characterized by <T>=0.56 ev corresponding to an excess energy of 2.1 eV above the dissociation threshold. NH+ fragments can be formed by two processes: the first one occurs at threshold and leads to NH+(X2Pi)+H2(X1Sigma+g); the second one is characterized by large KER values (up to 7 eV) and leads to either electronically excited NH+ or dissociation of H2. [less ▲]

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See detailReaction Dynamics of the Dichlorocarbene Anion Using tandem Mass Spectrometry.
Leyh, Bernard ULg; Mélon, Pierre

in Organic Mass Spectrometry (1993), 28

The dissociation dynamics of CCl2- anions were studied under various internal energy conditions. This study involved the measurement of daughter-ion spectra and branching ratios and of the amount of ... [more ▼]

The dissociation dynamics of CCl2- anions were studied under various internal energy conditions. This study involved the measurement of daughter-ion spectra and branching ratios and of the amount of kinetic energy released (KER) on the fragments. The competition between C and Cl loss for CCl2- ions created by many of the following sequence of processes: CCl4->CCl2+->(G=Xe, Kr C6H6)->CCl2--> fragments (1); CCl4->(CCl2--+[Cl,Cl]+;CCl2-; CCl2- (Ne)-> Fragments (2); CCl4->(CCl2)2+ (C6H6)->CCl2--> fragments (3) was particularly investigated. For process (1), the amount of fragmentating CCl2- ions is 8-10 times larger with Kr than with Xe or C6H6. The KER for Cl loss is smaller than 0.20 eV with the three target gases used. For the loss of C, the KER is much larger (0.7 eV). This KER is, however, equal to 0.21 eV for the collisionally activated C loss in process (2). For this latter process, the C loss vs Cl loss branching ratio decreases with increasing internal energy. The KERs measured for process (3) are vary similar to those obtained for process (1). It is suggested that repulsive or slightly bound excited states which correlate directly to the Cl2-(X2Sigma+)+C asymptote and which are vibronically coupled to the ground state play an important role in these dissociation processes. [less ▲]

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See detailUnimolecular reaction dynamics from Kinetic Energy Release Distributions. 1 - Dissociation of Bromobenzene Ions.
Lorquet, Jean-Claude ULg; Leyh, Bernard ULg

in Organic Mass Spectrometry (1993), 28

Preliminary data on a new method for extracting data from the kinetic energy release distribution of metastable fragment ions are presented. This method can give information concerning the energy ... [more ▼]

Preliminary data on a new method for extracting data from the kinetic energy release distribution of metastable fragment ions are presented. This method can give information concerning the energy threshold of the reaction and the energy dependence of the rate constant (i.e. its logarithmic derivative). It was applied to bromine loss from bromobenzene cations. [less ▲]

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See detailIon Translational Energy Distributions from Inner-shell Dissociative ionization of N2O, NH3 and SF6.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H. W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1992)

The IRPD method is applied to the dissociative ionization in the inner-shell ionization region for NO+, N2+, O+, N+ and N++/N2O. Particular attention has been focussed on the production and ion kientic ... [more ▼]

The IRPD method is applied to the dissociative ionization in the inner-shell ionization region for NO+, N2+, O+, N+ and N++/N2O. Particular attention has been focussed on the production and ion kientic energy distribution of H+/NH3. [less ▲]

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See detailPhotoionization of NH3 and its Isotopomers between 10 and 12 eV.
Locht, Robert ULg; Leyh, Bernard ULg; Denzer, W. et al

in Kistemaker, P. G.; Nibbering, N. M. (Eds.) Advances in Mass Spectrometry: Proceedings of the 12th IMSC, Amsterdam (International Mass Spectrometry Conference 26-30 August 1991): Book of Abstracts. (1991)

The photoionization of NH3 and its isotopomers is measured between 10-12 eV photon energy by using synchrotron radiation. The abundant autoionization structure observed in the ionization efficiency curves ... [more ▼]

The photoionization of NH3 and its isotopomers is measured between 10-12 eV photon energy by using synchrotron radiation. The abundant autoionization structure observed in the ionization efficiency curves is analyzed. [less ▲]

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