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See detailThe Photoionization Dynamics of Methyl Iodide (CH3I): a joint Photoelectron and Mass Spectrometric Investigation.
Locht, Robert ULg; Dehareng, Dominique ULg; Hottmann, K. et al

in Journal of Physics : B Atomic Molecular & Optical Physics (2010), 43(10), 105101

The threshold photoelectron (TPES) and the photoionization mass spectrometric (PIMS) study of CH3I in the 8-20 eV photon energy range are presented. The interpretation and assignments are supported by ab ... [more ▼]

The threshold photoelectron (TPES) and the photoionization mass spectrometric (PIMS) study of CH3I in the 8-20 eV photon energy range are presented. The interpretation and assignments are supported by ab initio calculations. The TPES shows many new discrete features in the Jahn-Teller split ground X 2E (2A'-2A”) state of CH3I+. A new continuous band starting at about 11.7 eV is detected. These observations are essentially correlated with autoionizing transitions. This interpretation is supported by constant ion state (CIS) spectroscopy. A large enhancement of the transitions to the A 2A and B 2E ionic states is ascribed to large autoionizing contributions. Based on the present calculations, the weak to very weak bands in the 18.0 eV-23.0 eV photon energy range are mainly assigned to 2a1-1 ionization and to double excitations corresponding essentially to the 2e-2 4a11 and 3a1- 1 2e-1 4a11 configurations. The photoionization mass spectrometric study allowed us to investigate in detail the ionization and dissociation of CH3I+ leading to CH2+, CH3+, I+ and CH2I+ from the threshold up to 20 eV photon energy. The experimental data are compared to ab initio calculated dissociation energies. The threshold of appearance of CH3+, I+ and CH2I+ fragments are concentrated in the 12.2-12.7 eV photon energy range. All three exit channels are correlated with the ground state of CH3I+ via nonadiabatic transitions. All three fragment ions have to appear through predissociation of the ionic X 2E state and autoionizing dissociation from the (2E3/2)6p Rydberg state. This interpretation is strongly supported by the photoabsorption spectrum measured recently in the same photon energy range [1]. At higher energies, beside direct or predissociation of the A 2A1 and B 2E states of CH3I+, autoionization is also suggested to contribute to the fragmentation in all decay channels. [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 detailThe Photoionization Mass Spectrometric Study of the Three membered Ring Systems C3H6, C2H4O and C2H4S and their open Chain Isomers.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H - on CD-ROM (2004)

The dissociative photoionization mass spectrometric study of C2H6, C2H4O and C2H4S has been measured using synchrotron radiation. The ionization efficiency curves of the molecular ions of the three ... [more ▼]

The dissociative photoionization mass spectrometric study of C2H6, C2H4O and C2H4S has been measured using synchrotron radiation. The ionization efficiency curves of the molecular ions of the three species are reported. [less ▲]

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See detailA photoionization mass spectrometric and threshold photoelectron-photoion coincidence study of vinylbromide (C2H3Br) in the vacuum ultraviolet range of 6-21 eV.
Hoxha, A.; Yu, S.-Y.; Locht, Robert ULg et al

in Chemical Physics (2011), 379(1-3), 99-108

The dissociative photoionization of vinyl bromide (C2H3Br) has been investigated by photoionization mass spectrometry (PIMS) and time-of-flight threshold photoelectron-photoion coincidence (TOF-TPEPICO ... [more ▼]

The dissociative photoionization of vinyl bromide (C2H3Br) has been investigated by photoionization mass spectrometry (PIMS) and time-of-flight threshold photoelectron-photoion coincidence (TOF-TPEPICO) spectrometry using synchrotron radiation. The photoionization efficiency curves of the three most abundant ions, i.e. C2H3Br+, C2H3+ and C2H2+, are measured and analyzed in detail. A C2H3+/Br- photoion-pair formation process has been detected for the first time. Some arguments are provided in favor of the electronic excitation of the C2H3+ fragment and of the isomerization of the C2H2+ ions. The breakdown diagram for these ions in the 9.8–21 eV photon energy range, derived from TOF-TPEPICO mass spectra, is discussed. The involvement of the successive C2H3Br+ ionic states and the role of autoionization of C2H3Br Rydberg states are emphasized. For the two minor HBr+ and Br+ fragment ions only the breakdown diagrams are measured and appearance energies are derived. [less ▲]

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See detailPhotoionization Mass Spectrometry of Kinetic energy-selected ions. An Ion Retarding Potential Difference method applied to NO+ and O+ from N2O.
Locht, Robert ULg; Hagenow, G.; Hottmann, K. et al

in Chemical Physics (1991), 151

A new method is described to obtain photoionization efficiency curves of kinetic energy-selected fragment ions. The method is tested and discussed in the case of the dissociative photoionization yields of ... [more ▼]

A new method is described to obtain photoionization efficiency curves of kinetic energy-selected fragment ions. The method is tested and discussed in the case of the dissociative photoionization yields of NO+ and O+ from N2O. The attention is focussed on the dissociative autoionization processes in the threshold region, in the Franck-Condon region of the N2O(A2Sigma+) state and in the Franck-Condon gap between the A2Sigma+ and B2Pi states. [less ▲]

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See detailPhotoionization Mass Spectrometry of Kinetic Energy-selected ions. The Translational Energy Distribution of N+/N2 in the Inner-shell Ionization energy range.
Locht, Robert ULg; Denzer, W.; Rühl, E. et al

in Chemical Physics (1992), 160

An ion retarding potential difference (IRPD) method has been used to investigate the ion yield and the kinetic energy distributions of N+/N2 produced by photoionization mass spectrometry using synchrotron ... [more ▼]

An ion retarding potential difference (IRPD) method has been used to investigate the ion yield and the kinetic energy distributions of N+/N2 produced by photoionization mass spectrometry using synchrotron radiation. Photoion yield curves of energy selected N+ ions are deduced. Translational energy distributions of N+ at the energies of the N(1s)->pi*, N(1s)->(nl)1 and above the N(1s)-1 threshold are determined. Comparison is made with previous photoion-photoelectron coincidence work using time-of-flight (TOF) measurements. [less ▲]

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See detailPhotoionization modeling of oxygen K absorption in the interstellar medium : the Chandra grating spectra of XTE J1817-330
Gatuzz, E; Garcia, J; Mendoza, C et al

in Astrophysical Journal (2013), 768

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See detailThe Photoionization of Ammonia Revisited. The Autoionization in NH3 and its three Isotopomers in the 10-12 eV photon energy range.
Locht, Robert ULg; Leyh, Bernard ULg; Denzer, W. et al

Book published by Berliner Elektronen Speicherring für Synchrotron Strahlung m.b.H (1990)

The photoionization efficiency curves of NH3, NH2D, NHD2 and ND3 have been measured using synchrotron radiation. The fine structure has been interpreted in terms of vibrational autoionization.

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See detailThe Photoionization of Ammonia revisited. The Vibrational Autoionization of NH3 and its three Isotopomers in the 10-12 eV photon energy range.
Locht, Robert ULg; Leyh, Bernard ULg; Denzer, W. et al

in Chemical Physics (1991), 155

The photoionzation efficiency curves of NH3 and its three isotopomers have been investigated in the photon energy range of the first ionized state. From the analysis of the corresponding vibrational ... [more ▼]

The photoionzation efficiency curves of NH3 and its three isotopomers have been investigated in the photon energy range of the first ionized state. From the analysis of the corresponding vibrational structure, wavenumbers and anharmonicity constants are deduced. The detailed investigation of the abundant autoionization structure tends to show the adiabatic ionization energy to be 10.072+/-0.010 eV for NH3, NH2D and NHD2 and 10.083+/-0.010 eV for ND3. All autoionization features were classified in vibrational progressions (nu2 bending mode) belonging to nasa1 (or nd) and npe (n=5, 6, 7) Rydberg series. Vibrational autoionization occurs through Delta v transitions up to -9. A qualitative analysis of the intensity distribution of these series strongly supports that transitions involving odd Delta v values are favoured. This observation can be understood by applying group theoretical considerations to the theory of vibrational autoionization. [less ▲]

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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 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 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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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 detailPhotoionization of tryptophan: An electron spin resonnance investigation
Hoebeke, Maryse ULg; Gandin, E.; Lion, Y.

in Photochemistry & Photobiology (1986), 44

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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 detailPhotolangage
Partoune, Christine ULg

Learning material (2010)

Comme son nom le laisse deviner, l’outil "Photolangage" a pour but de faciliter l’expression de chacun en partant de photos qui ont une signification symbolique. Cette entrée en matière par l’image avant ... [more ▼]

Comme son nom le laisse deviner, l’outil "Photolangage" a pour but de faciliter l’expression de chacun en partant de photos qui ont une signification symbolique. Cette entrée en matière par l’image avant la parole est de nature à redistribuer les rapports de force habituels dans un groupe. L’objectif n’est pas de s’affronter, ou de chercher à se convaincre, ou de savoir qui a raison. Il est de se découvrir soi-même, de se rendre compte de son propre point de vue par rapport au thème. [less ▲]

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See detailPhotometric accuracy - The impact of extrapolation in differing color-transformation schemes
Manfroid, Jean ULg; Sterken, C.; Gosset, Eric ULg

in Astronomy and Astrophysics (1992), 264

We discuss photometric errors that arise from the use of differing color-transformation schemes when extrapolating outside the range of the standard values that define the system. An example based on data ... [more ▼]

We discuss photometric errors that arise from the use of differing color-transformation schemes when extrapolating outside the range of the standard values that define the system. An example based on data from the Long-Term Photometry of Variables project (LTPV) at ESO is analyzed. Practically, the extrapolation errors are most evident as systematic brightness jumps of some program stars, seen when monitored over several observing runs. Conclusions are drawn about the choice of standard stars in the Stromgren system. [less ▲]

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See detailA photometric and spectroscopic investigation of star formation in the very young open cluster NGC 6383
Rauw, Grégor ULg; Manfroid, Jean ULg; De Becker, Michaël ULg

in Astronomy and Astrophysics (2010), 511

Context. The very young open cluster NGC 6383 centered on the O-star binary HD 159176 is an interesting place for studying the impact of early-type stars with strong radiation fields and powerful winds on ... [more ▼]

Context. The very young open cluster NGC 6383 centered on the O-star binary HD 159176 is an interesting place for studying the impact of early-type stars with strong radiation fields and powerful winds on the formation processes of low-mass stars. <BR /> Aims: To investigate this process, it is necessary to determine the characteristics (age, presence, or absence of circumstellar material) of the population of low-mass pre-main-sequence (PMS) stars in the cluster. <BR /> Methods: We obtained deep UBV(RI)[SUB]c[/SUB] Hα photometric data of the entire cluster as well as medium-resolution optical spectroscopy of a subsample of X-ray selected objects. <BR /> Results: Our spectroscopic data reveal only very weak Hα emission lines in a few X-ray selected PMS candidates. We photometrically identify a number of Hα emission candidates but their cluster membership is uncertain. We find that the fainter objects in the field of view have a wide range of extinction (up to A[SUB]V[/SUB] = 20), one X-ray selected OB star having A[SUB]V[/SUB] â 8. <BR /> Conclusions: Our investigation uncovers a population of PMS stars in NGC 6383 that are probably coeval with HD 159176. In addition, we detect a population of reddened objects that are probably located at different depths within the natal molecular cloud of the cluster. Finally, we identify a rather complex spatial distribution of Hα emitters, which is probably indicative of a severe contamination by foreground and background stars. Based on observations collected at the European Southern Observatory (ESO, La Silla, Chile).Table 2 is only available in electronic form at the CDS via anonymous ftp cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A25">http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A25</A> [less ▲]

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See detailA photometric classification of Wolf-Rayet stars
Vreux, Jean-Marie ULg; Manfroid, Jean ULg; Royer, P.

in Liege International Astrophysical Colloquia (1996)

Not Available

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See detailPhotometric measurements of the O2 U.V. nightglow
Gérard, Jean-Claude ULg

in Planetary and Space Science (1975), 23

The O2 Herzberg system in the night airglow was measured in the wavelength range 2400 to 3100 A by the S2/68 UV telescope aboard the ESRO TD-1 satellite. The statistical latitudinal variations of the ... [more ▼]

The O2 Herzberg system in the night airglow was measured in the wavelength range 2400 to 3100 A by the S2/68 UV telescope aboard the ESRO TD-1 satellite. The statistical latitudinal variations of the slant emissional rates are analysed; auroral contamination by other emissions was eliminated from the data by monitoring the light levels in the other channels of the experiment. The slant emission rate varies from 3.5 to 15 kR, indicating an irregular structure of the atomic oxygen near the turbopause. A maximum average intensity occurrs near the tropics in the winter hemisphere. The observed emission rate is accounted for quantitatively by the three-body recombination of atmospheric oxygen using an estimated 20 per cent production efficiency for the A(3) sigma state, if quenching by N2 occurrs at the rate approximated from the relative statistical weight of the A state. [less ▲]

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