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See detailThe Vacuum UV photoabsorption spectroscopy of the geminal ethylene difluoride (1,1-C2H2F2). The vibrational structure and its analysis.
Locht, Robert ULiege; Jochims, H.W.; Leyh, Bernard ULiege

in Chemical Physics (2012), 405

The vacuum UV photoabsorption spectrum of 1,1-C2H2F2 has been examined in detail between 6 eV and 25 eV photon energy by using synchrotron radiation. The broad band observed at 7.52 eV includes the →∗ and ... [more ▼]

The vacuum UV photoabsorption spectrum of 1,1-C2H2F2 has been examined in detail between 6 eV and 25 eV photon energy by using synchrotron radiation. The broad band observed at 7.52 eV includes the →∗ and the 2b1→3s Rydberg transitions. An analysis is proposed and applied to the fine structure belonging to these transitions. For the (2b1)→∗ transition, one long vibrational progression is observed with ω2=1 475±80 cm-1 combined with one quantum of vibration of ω4= 976±24 cm-1 and its adiabatic excitation energy is determined at 6.742 eV. The 2b1→3s Rydberg transition is characterized by a single progression with ω2=1532±80 cm-1 starting at 6.957 eV. These vibrations are ascribed to the C=C and C-F stretching motions respectively. The abundant structure observed between 8.2 eV and 11.2 eV has been analyzed in terms of vibronic transitions to ns (δ= 0.98) and two different np (δ= 0.50 and 0.31) and nd (δ= 0.13 and 0.044) Rydberg series all converging to the 1,1-C2H2F2+(B1) ionic ground state. An analysis of the associated vibrational structure of the individual Rydberg states has been attempted providing average values of the wavenumbers ω2= 1 549±16 cm-1, ω4= 839±40 cm-1 and ω5= 589±16 cm-1. Eight other Rydberg states were also analyzed. The vacuum UV spectrum of 1,1-C2H2F2 has been recorded for the first time above 11.2 eV and up to 25 eV. Several broad and strong bands are tentatively assigned to transitions to Rydberg states which are members of Rydberg series converging to excited ionic states of 1,1-C2H2F2. For several of these Rydberg states vibrational, structures are observed and assignments are proposed. [less ▲]

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See detailThe Spectroscopy of the Geminal Ethylene difluoride (1,1-C2H2F2): HeI, threshold and Constant Ion State spectroscopies.
Locht, Robert ULiege; Dehareng, Dominique ULiege; Leyh, Bernard ULiege

in Journal of Physics : B Atomic Molecular & Optical Physics (2012), 45(11), 115101

The threshold photoelectron spectrum (TPES) and the constant ion state (CIS) spectra of the individual ionic states of 1,1-C2H2F2 have been recorded using synchrotron radiation. The TPES has been measured ... [more ▼]

The threshold photoelectron spectrum (TPES) and the constant ion state (CIS) spectra of the individual ionic states of 1,1-C2H2F2 have been recorded using synchrotron radiation. The TPES has been measured between 9.5 eV and 28 eV photon energy. For comparison the HeI photoelectron spectrum (HeI-PES) has also been measured and analyzed in detail. Numerous vibrational structures, reported for the first time, observed in the ground state and the seven excited states of the cation are analyzed. Quantum chemical calculations have been performed and provided support to the assignments. The exceptional contribution of autoionization to the HeI PES could be emphasized. State selected CIS spectra highlighted the importance of the autoionizing contribution to the production of almost all ionized states of 1,1-C2H2F2 observed in this work. Several peculiarities of the vibrationally resolved CIS spectra are analyzed. [less ▲]

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See detailA combination of ESR and SANS techniques to explore the cyclodextrin action on membranes
Grammenos, Angeliki ULiege; Joset, Arnaud ULiege; Leyh, Bernard ULiege et al

in Current Medicinal Chemistry (2011)

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See detailProbing DNA interactions with gold
Bano, F; Leyh, Bernard ULiege; De Pauw, Edwin ULiege et al

Conference (2011)

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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 ULiege 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 detailGas Phase Fullerene Anions Hydrogenation by Methanol Followed by IRMPA Dehydrogenation
Greisch, Jean-François ULiege; Leyh, Bernard ULiege; Remacle, Françoise ULiege et al

in Journal of the American Society for Mass Spectrometry (2010), 21(1), 117-126

The characterization in the gas phase of the mechanisms responsible for hydride formation can <br />contribute to the development of new materials for hydrogen storage. The present work <br />provides ... [more ▼]

The characterization in the gas phase of the mechanisms responsible for hydride formation can <br />contribute to the development of new materials for hydrogen storage. The present work <br />provides evidence of a hydrogenation-dehydrogenation catalytic cycle for C60 anions in the <br />gas phase using methanol vapor at room temperature as hydrogen donor. [less ▲]

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See detailThe Photoionization Dynamics of Methyl Iodide (CH3I): a joint Photoelectron and Mass Spectrometric Investigation.
Locht, Robert ULiege; Dehareng, Dominique ULiege; 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 detailA Photoelectron Spectroscopic Investigation of Vinyl Fluoride (C2H3F). The HeI, Threshold and CIS Photoelectron Spectroscopy.
Locht, Robert ULiege; Leyh, Bernard ULiege; Dehareng, Dominique ULiege et al

in Journal of Physics : B Atomic Molecular & Optical Physics (2010), 43(1), 01510215

The threshold photoelectron spectrum (TPES) and the constant ion state (CIS) spectra of the individual ionic states of C2H3F have been recorded using synchrotron radiation. For comparison a well resolved ... [more ▼]

The threshold photoelectron spectrum (TPES) and the constant ion state (CIS) spectra of the individual ionic states of C2H3F have been recorded using synchrotron radiation. For comparison a well resolved HeI photoelectron spectrum (HeI-PES) has also been measured and analyzed in detail. The TPES has been measured between 9.5 eV and 35 eV photon energy. Numerous vibrational structures, reported for the first time, observed in the ground state and the six excited states of the cation are analyzed. Quantum chemical calculations have been performed and provide strong support to the assignments. State selected CIS spectra highlighted the major importance of autoionization for the production of almost all ionized states of C2H3F observed in this work. [less ▲]

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See detailThe Vacuum UV photoabsorption spectroscopy of Vinyl Fluoride (C2H3F): The vibrational fine structure and its analysis.
Locht, Robert ULiege; Leyh, Bernard ULiege; Dehareng, Dominique ULiege et al

in Chemical Physics (2009), 362(3), 97-108

The vacuum UV photoabsorption spectrum of C2H3F has been examined in detail between 6 eV and 25 eV photon energy by using synchrotron radiation. The analysis of the data is supported by ab initio quantum ... [more ▼]

The vacuum UV photoabsorption spectrum of C2H3F has been examined in detail between 6 eV and 25 eV photon energy by using synchrotron radiation. The analysis of the data is supported by ab initio quantum mechanical calculations applied to valence and Rydberg excited states of C2H3F. At 7.6 eV the pi-pi* and the 2a"->3s transitions are observed. An analysis is proposed and applied to the mixed fine structure belonging to these transitions. For the pi->pi* transition one single long vibrational progression is observed with hcwe= 95±7 meV (766±56 cm-1) and its adiabatic excitation energy is 6.892 eV (55 588 cm-1). The 2a"->3s transition is characterized by a single short progression with hc e= 167±10 meV (1 350±80 cm-1)starting at 6.974 eV (56 249 cm-1). From the present ab initio calculations these two wavenumbers best correspond to the vibrational modes v9 (CH2 rock in-plane, FCCbend) and v6 (CH2 rock in-plane, CF stretch) calculated at 615 cm-1 in the pi* state and 1 315 cm-1 in the (2A")3s Rydberg state respectively. The C=C stretching could not be excluded. The dense structured spectrum observed between 8.0 eV and 10.5 eV has been analyzed in terms of vibronic transitions to Rydberg states all converging to the C2H3F+(X2A") ionic ground state. An analysis of the associated complex fine structure of the individual Rydberg states has been attempted providing average values of the wavenumbers, e.g., for the (2A")3p Rydberg state hcw9= 60±1 meV (or 484±8 cm-1), hcw7= 151±7 meV (or 1 218±60 cm-1), hcw4= 191±3 meV (or 1 540±24 cm-1). The assignment of hcw= 105±5 meV (or 823±40 cm-1) is discussed. These experimental values are in good agreement with the theoretical predictions for C2H3F+ [R. Locht, B. Leyh, D. Dehareng, K. Hottmann, H. Baumgärtel, Chem.Phys. (in press)]. Above 10.5 eV and up to 25 eV several broad and strong bands are tentatively assigned to transitions to valence (V-V) and/or Rydberg (V-R) states converging to excited ionic states of C2H3F. [less ▲]

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See detailpH-sensitive micellar systems for controlled drug delivery: synthesis and structural characterization by small-angle neutron scattering
Joset, Arnaud ULiege; Jérôme, Christine ULiege; Brulet, Annie et al

Poster (2009, May 14)

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in ... [more ▼]

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in drug delivery applications to fight cancer1. The hydrophobic polycaprolactone (PCL) core is intended to incorporate the drug. The corona of hydrophilic polyethylene oxide (PEO) stabilizes the nanocarriers with respect to the plasma proteins. The pH in the neighborhood of the tumoral cells is lower than in the healthy cells. We incorporated a pH-sensitive sequence of poly(2-vinylpyridine) (P2VP). As a result, these micelles are expected to deliver their drug near the cancerous cells without affecting the healthy cells. When the pH is acidic, the P2VP is protonated and the chains are repulsive. The micellar size is then larger than in basic pH, when the P2VP is precipitated on the PCL core. We prepared PCL65-b-P2VP31 / PCL65-b-PEO114 and PCL32-b-P2VP52 / PCL36-b-PEO114 50:50 mixtures of diblocks copolymers. The resulting mixed micelles are analyzed by SANS. We developed a theoretical model with a spherical water-free PCL core. The PEO corona is described as consisting of gaussian chains with a thickness estimated as twice the chain gyration radius, Rg. We propose two alternatives for handling the P2VP zone. The P2VP molecules are either assumed to be Gaussian chains or they fill a shell of thickness L with possible water penetration.The fitting of the models to the experimental scattering cross sections leads to important structural parameters like the aggregation number, the core radius, the gyration radius and the thickness of the P2VP shell. [less ▲]

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See detailpH-sensitive micellar systems for controlled drug delivery: synthesis and structural characterization by small-angle neutron scattering
Joset, Arnaud ULiege; Jérôme, Christine ULiege; Brulet, Annie et al

Poster (2009, March)

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in ... [more ▼]

The aim of the project is the preparation of micellar nanocarriers made of biocompatibles copolymers and their structural analysis by Small Angle Neutron Scattering (SANS). These micelles could be used in drug delivery applications to fight cancer1. The hydrophobic polycaprolactone (PCL) core is intended to incorporate the drug. The corona of hydrophilic polyethylene oxide (PEO) stabilizes the nanocarriers with respect to the plasma proteins. The pH in the neighborhood of the tumoral cells is lower than in the healthy cells. We incorporated a pH-sensitive sequence of poly(2-vinylpyridine) (P2VP). As a result, these micelles are expected to deliver their drug near the cancerous cells without affecting the healthy cells. When the pH is acidic, the P2VP is protonated and the chains are repulsive. The micellar size is then larger than in basic pH, when the P2VP is precipitated on the PCL core. We prepared PCL65-b-P2VP31 / PCL65-b-PEO114 and PCL32-b-P2VP52 / PCL36-b-PEO114 50:50 mixtures of diblocks copolymers. The resulting mixed micelles are analyzed by SANS. We developed a theoretical model with a spherical water-free PCL core. The PEO corona is described as consisting of gaussian chains with a thickness estimated as twice the chain gyration radius, Rg. We propose two alternatives for handling the P2VP zone. The P2VP molecules are either assumed to be Gaussian chains or they fill a shell of thickness L with possible water penetration.The fitting of the models to the experimental scattering cross sections leads to important structural parameters like the aggregation number, the core radius, the gyration radius and the thickness of the P2VP shell. [less ▲]

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See detailCollision induced dissociation of deuterium enriched protonated 2'-deoxyguanosine
Greisch, Jean-François ULiege; Leyh, Bernard ULiege; De Pauw, Edwin ULiege

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2009), 51(1), 89-96

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose ... [more ▼]

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose, [ bH(2)]. The origin of the hydrogen transfer for the protonated 2'-deoxyguanosine has been investigated by collision induced dissociation of deuterium enriched molecules. [ 1'-H-2] 2'-deoxyguanosine, [ 2',2aEuro(3)-H-2(2)] 2'-deoxyguanosine, and [ 5',5aEuro(3)-H-2(2)] 2'-deoxyguanosine have been studied and deuterium/hydrogen back exchange has been used following complete or partial exchange of the 2'-deoxyguanosine in solution. Based on the fragmentation of the deuterated molecular ions, the hydrogen transferred from the 2'-deoxyribose to the guanine is found to originate from the O5' atom on the 2'-deoxyribose. A fragmentation mechanism involving a hydrogen shift from the 2' position to the oxygen atom O5' and supported by the kinetic isotope effect on the survival yield curves is proposed. The influence of the 2'-deoxyguanosine conformation on the hydrogen transfer and the fragmentation mechanism is discussed. [less ▲]

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