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See detailA Photoelectron Spectroscopic Investigation of Vinyl Fluoride (C2H3F). The HeI, Threshold and CIS Photoelectron Spectroscopy.
Locht, Robert ULg; Leyh, Bernard ULg; Dehareng, Dominique ULg 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 ULg; Leyh, Bernard ULg; Dehareng, Dominique ULg 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 ULg; Jérôme, Christine ULg; 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 ULg; Jérôme, Christine ULg; 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 ULg; Leyh, Bernard ULg; De Pauw, Edwin ULg

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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See detailLes valeurs et l'école. Atelier n°6
Gilles, Jean-Luc ULg; Leyh, Bernard ULg; Voos, Marie-Catherine ULg

in Puzzle (2009), 25

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See detailMedium and High Resolution Vacuum UV Photoabsorption Spectroscopy of Methyl Iodide (CH3I) and its deuterated isotopomers CD3I and CH2DI. A Rydberg series Analysis.
Locht, Robert ULg; Leyh, Bernard ULg; Jochims, H.-W. et al

in Chemical Physics (2009), 365(3), 109-128

The vacuum UV photoabsorption spectrum of CH3I has been investigated between 5 and 20 eV. Numerous vibronic transitions are observed. In the high 10-20 eV photon energy range weak to very weak diffuse ... [more ▼]

The vacuum UV photoabsorption spectrum of CH3I has been investigated between 5 and 20 eV. Numerous vibronic transitions are observed. In the high 10-20 eV photon energy range weak to very weak diffuse bands are observed and ascribed to electronic transitions from 3a1, 1e and 2a1 to Rydberg orbitals. In the 6-10.5 eV photon energy range more than 200 sharp and strong to weak lines have been observed. Several photon energy ranges were explored under high resolution conditions allowing us to observe many series up to high values of the principal quantum number n. They are assigned to vibrationless Rydberg transitions and classified into two groups converging to the two components of the spin-orbit split 2E state of CH3I+. These two groups consist of six different Rydberg series, i.e., nsa1, npa1, npe, nda1, nde and nf. A very close correlation has been established between the term values of the Rydberg states in CH3I and in Xe for ns, np, nd and nf Rydberg transitions. For the first time, the same measurements have been performed and the interpretation has been proposed for the photoabsorption spectrum of CH2DI and CD3I in the 6-10.5 eV photon energy range. For these two species, ionization energies are deduced: for the 2E3/2 and 2E1/2 states of CH2DI, these are IEad=9.544 eV and IEad=10.168 eV respectively and the corresponding energies are 9.552 eV and 10.173 eV in CD3I. [less ▲]

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See detailDetection of Oligonucleotide Gas-Phase Conformers: H/D Exchange and Ion Mobility as Complementary Techniques
Balbeur, Dorothée ULg; Widart, Joëlle ULg; Leyh, Bernard ULg et al

in Journal of the American Society for Mass Spectrometry (2008), 19(7), 938-946

Gas-phase hydrogen/deuterium exchange of small oligonucleotides (dTG, dC6 and C6) with CD3OD was performed in the second hexapole of a Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer ... [more ▼]

Gas-phase hydrogen/deuterium exchange of small oligonucleotides (dTG, dC6 and C6) with CD3OD was performed in the second hexapole of a Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer. Ion activation experiments were conducted by accelerating the ions at the entrance of the H/D exchange cell under conditions promoting exclusively collisional isomerization. These experiments allowed us to assess the presence of several conformers, and to probe the height of the isomerization barrier separating these conformers. Ion mobility experiments were also performed. Their results were consistent with the H/D exchange data. A model accounting for the competing isomerization and H/D exchange reactions is proposed. Comparing the ion acceleration experiments for H/D exchange and for ion mobility reveals that the most compact conformer displays the fastest H/D exchange. This observation shows that H/D exchange and ion mobility provide us with complementary information because hydrogen accessibility and macromolecule compactness are not univocally associated. [less ▲]

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See detailCore-Shell-Corona Micelles by PS-b-P2VP-b-PEO Copolymers: Focus on the Water-Induced Micellization Process
Willet, Nicolas ULg; Gohy, Jean-François; Auvray, Loïc et al

in Langmuir (2008), 24(7), 3009-3015

It is now well established that amphiphilic PS-b-P2VP-b-PEO linear triblock copolymers can form multilayered assemblies, thus core-shell-corona (CSC) micelles, in water. Micellization is triggered by ... [more ▼]

It is now well established that amphiphilic PS-b-P2VP-b-PEO linear triblock copolymers can form multilayered assemblies, thus core-shell-corona (CSC) micelles, in water. Micellization is triggered by addition of a small amount of water into a dilute solution of the PS-b-P2VP-b-PEO copolymer in a non-selective organic solvent. However, the phenomena that take place at the very beginning of this process are poorly documented. How these copolymer chains are perturbed by addition of water was investigated in this work by light and neutron scattering techniques and transmission electron microscopy. It was accordingly possible to determine the critical water concentration (CWC), the compactness of the nano-objects in solution, their number of aggregation, and their hydrodynamic diameter at each step of the micellization process. [less ▲]

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See detailMass Spectrometric Study of the Ionized C60: (Gamma-Cyclodextrin)2 Inclusion Complex by Collision Induced Dissociation
Greisch, Jean-François ULg; Kyritsoglou, S.; Leyh, Bernard ULg et al

in Journal of Mass Spectrometry [=JMS] (2008), 43(2), 242-50

The water soluble inclusion complex [C(60):(gamma-cyclodextrin)(2)] has been characterized using electrospray tandem mass spectrometry and collision induced dissociation. [C(60):(gamma-cyclodextrin)(2 ... [more ▼]

The water soluble inclusion complex [C(60):(gamma-cyclodextrin)(2)] has been characterized using electrospray tandem mass spectrometry and collision induced dissociation. [C(60):(gamma-cyclodextrin)(2)] ions were detected in the gas phase as doubly deprotonated, doubly protonated and doubly sodiated ions. The absence of monocharged complex ions following electronebulization is a likely consequence of the dimeric nature and structural symmetry of the inclusion complex. The collision induced dissociation of positive ions led exclusively to the observation of the protonated and sodiated cyclodextrin ions as well as their fragments. In negative ion mode the closed shell anion C(60)H(-) was the dominant fragment detected at low collision energies whereas at higher collision energies the signal corresponding to deprotonated cyclodextrin units becomes significant. Since C(60) (2-) has been reported to have a nonnegligible basicity compared to C(60) and C(60) (-), it is likely that the proton transfer involved in the formation of the C(60)H(-) anion occurs following transfer of the two electrons from the deprotonated gamma-cyclodextrins to the fullerene. Finally, the charge state of the inclusion complex ions is also shown to affect the interaction strengths between its subunits. The relative stabilities of the three ionic species studied in gas phase following electronebulization are as follows: [C(60):(gamma-cyclodextrin)(2) + 2H](2+) < [C(60):(gamma-cyclodextrin)(2)- 2H](2-) < [C(60):(gamma-cyclodextrin)(2) + 2Na](2+). [less ▲]

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See detailThe Role of Long-Range Forces in the Determination of Translational Kinetic Energy Release. Loss of C4H4+ from Benzene and Pyridine Cations.
Gridelet, E.; Locht, Robert ULg; Lorquet, Andrée ULg et al

in Journal of Physical Chemistry A (2008), 112

Kinetic energy release distributions (KERDs) for the benzene ion fragmenting into C4H4+ and C2H2 have been recorded by double-focussing mass spectrometry in the metastable energy window and by a retarding ... [more ▼]

Kinetic energy release distributions (KERDs) for the benzene ion fragmenting into C4H4+ and C2H2 have been recorded by double-focussing mass spectrometry in the metastable energy window and by a retarding field experiment up to an energy of 5 eV above the fragmentation threshold. They are compared with those resulting from the HCN loss reaction from the pyridine ion. Both reactions display a similar variation of the kinetic energy release as a function of the internal energy: the average release is smaller than statistically expected, with a further restriction of the phase-space sampling for the C5H5N+ dissociation. Ab initio calculations of the potential-energy profile have been carried out. They reveal a complicated reaction mechanism, the last step of which consists in the dissociation of a weakly bound ion-quadrupole or ion-dipole complex. The KERDs have been analyzed by the maximum entropy method. The fraction of phase-space effectively sampled by the pair of fragments has been determined and is similar for both dissociations. Both reactions are constrained by the square root of the released kinetic energy, epsilon1/2. This indicates that in the latter stage of the dissociation process, the reaction coordinate is adiabatically decoupled from the bath of the bound degrees of freedom. For the C6H6+ fragmentation, the analysis of the experimental results strongly suggests that, just as for the symmetric interaction potential, the translational motion is confined to a two-dimensional subspace. This dimensionality reduction of the translational phase space is due to the fact that the Hamiltonian of both weakly bound complexes contains a cyclic coordinate. [less ▲]

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See detailFast multiresponsive micellar gels from a smart ABC triblock copolymer
Willet, Nicolas ULg; Gohy, Jean-François; Lei, Liangcai et al

in Angewandte Chemie (International ed. in English) (2007), 46(42), 7988-7992

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and ... [more ▼]

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and shearing. The gel has a hierarchical structure with spherical core-shell-corona micelles, which, in turn, pack closely into an ordered cubic structure. [less ▲]

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See detailpH-responsive micelles in dilute and gel-like media
Willet, Nicolas ULg; Leyh, Bernard ULg; Gohy, Jean-François et al

Conference (2006, June)

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