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Valérie Vallet

Bio: Valérie Vallet is an academic researcher from university of lille. The author has contributed to research in topics: Uranyl & Ab initio. The author has an hindex of 28, co-authored 124 publications receiving 3176 citations. Previous affiliations of Valérie Vallet include Royal Institute of Technology & Lille University of Science and Technology.


Papers
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Journal ArticleDOI
TL;DR: A review on the combination of experimental and theoretical methods to obtain microscopic information on the chemistry of actinides in aqueous solution can be found in this article, where a comparison of experimental data with those obtained using quantum chemical methods is provided.

173 citations

Journal ArticleDOI
TL;DR: In this article, a model of the photoinduced hydrogen elimination reaction in phenol via the conical intersections of the dissociative π1σ* state with the π 1π* state and the electronic ground state has been investigated by time-dependent quantum wavepacket calculations.
Abstract: The photoinduced hydrogen elimination reaction in phenol via the conical intersections of the dissociative π1σ* state with the π1π* state and the electronic ground state has been investigated by time-dependent quantum wave-packet calculations. A model including three intersecting electronic potential-energy surfaces (S0, π1σ*, and π1π*) and two nuclear degrees of freedom (OH stretching and OH torsion) has been constructed on the basis of accurate ab initio multireference electronic-structure data. The electronic population transfer processes at the conical intersections, the branching ratio between the two dissociation channels, and their dependence on the initial vibrational levels have been investigated by photoexciting phenol from different vibrational levels of its ground electronic state. The nonadiabatic transitions between the excited states and the ground state occur on a time scale of a few tens of femtoseconds if the π1π*‐π1σ* conical intersection is directly accessible, which requires the excitation of at least one quantum of the OH stretching mode in the π1π* state. It is shown that the node structure, which is imposed on the nuclear wave packet by the initial preparation as well as by the transition through the first conical intersection (π1π*‐π1σ*), has a profound effect on the nonadiabatic dynamics at the second conical intersection (π1σ*‐S0). These findings suggest that laser control of the photodissociation of phenol via IR mode-specific excitation of vibrational levels in the electronic ground state should be possible.

171 citations

Journal ArticleDOI
TL;DR: In this paper, the structures of the UO2(aq)2+ ion and of the uranium(VI) hydroxide complex(es) formed in strongly alkaline solution have been investigated theoretically using molecular-orbital based quantum chemical methods, and experimentally using EXAFS methodology.
Abstract: The structures of the UO2(aq)2+ ion and of the uranium(VI) hydroxide complex(es) formed in strongly alkaline solution have been investigated theoretically using molecular-orbital based quantum chemical methods, and experimentally using EXAFS methodology. Relativity was included explicitly through the Douglas−Kroll transformation. The uranium atom was described at the ECP level, using the AIMP methodology. The structures of [UO2(H2O)5]2+, and the hydroxide complexes, viz., [UO2(OH)4·(H2O)]2-, [UO2(OH)4]2-·(H2O), [UO2(O)(OH)2]2-·2(H2O), and [UO2(OH)5]3-, were optimized at the SCF level, using gradient techniques, while the relative stabilities were calculated at the MP2 level of approximation. The third structure contains three coordinated ligands, one of which is an oxide ion, in the plane perpendicular to the linear UO2-unit. Complexes of this type have not been experimentally identified for U(VI); however, they are formed for the iso-electronic Np(VII). The experimental EXAFS data indicates that the comp...

167 citations

Journal ArticleDOI
TL;DR: In this article, a two-step uncracted spin-orbit configuration interaction (CI) method was proposed to automatically account for spinorbit polarization effects on multiconfigurational wave functions by selecting the single excitations having a significant spinorbit interaction with a chosen determinantal reference space.
Abstract: We present a new two-step uncontracted spin-orbit configuration interaction (CI) method which automatically accounts for spin-orbit polarization effects on multiconfigurational wave functions by selecting the single excitations having a significant spin-orbit interaction with a chosen determinantal reference space. This approach is in the line of a conventional two-step method, as a sophisticated correlation treatment in a scalar relativistic approximation is carried out in the first step. In the second step, we define a model space which includes a set of reference configurations able to represent all the wanted states along with singly excited configurations selected with the spin-orbit (SO) operator. We then exploit the first-step calculation in order to include correlation effects via an effective Hamiltonian technique and diagonalize the full matrix on the determinantal basis. The method combines the advantages of both one-step and conventional two-step SO–CI methods; it intends to treat efficiently the cases where both relativity and extended CI treatments are needed. The new code EPCISO is tested on the spin-orbit splitting of the 2P electronic ground state of the thallium atom which, in spite of its very simple electronic structure is a well-known difficult case study for SO–CI methods. The EPCISO code yields results in excellent agreement with the experimental splitting value; they are compared to those obtained using the conventional two-step CIPSO code.

142 citations

Journal ArticleDOI
TL;DR: Solvent effects were shown to give the main contribution to the observed structure variations between the uranium(VI) tetrahydroxide and the tetrafluoride complexes.
Abstract: The structures of the complexes UO2Fn(H2O)5-n2-n, n = 3−5, have been studied by EXAFS. All have pentagonal bipyramid geometry with U−F of and U−H2O distances equal to 2.26 and 2.48 A, respectively. On the other hand the complex UO2(OH)42- has a square bipyramid geometry both in the solid state and in solution. The structures of hydroxide and fluoride complexes have also been investigated with wave function based and DFT methods in order to explore the possible reasons for the observed structural differences. These studies include models that describe the solvent by using a discrete second coordination sphere, a model with a spherical, or shape-adapted cavity in a conductor-like polarizable continuum medium (CPCM), or a combination of the two. Solvent effects were shown to give the main contribution to the observed structure variations between the uranium(VI) tetrahydroxide and the tetrafluoride complexes. Without a solvent model both UO2(OH)4(H2O)2- and UO2F4(H2O)2- have the same square bipyramid geometry...

137 citations


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01 Jan 2016
TL;DR: The principles of fluorescence spectroscopy is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can download it instantly.
Abstract: Thank you very much for downloading principles of fluorescence spectroscopy. As you may know, people have look hundreds times for their favorite novels like this principles of fluorescence spectroscopy, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some harmful bugs inside their desktop computer. principles of fluorescence spectroscopy is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the principles of fluorescence spectroscopy is universally compatible with any devices to read.

2,960 citations

01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations

Journal ArticleDOI
TL;DR: In this paper, a set of lanthanide pseudopotentials of the Stuttgart-Bonn variety has been supplemented by corresponding potentials for lanthanum and lutetium in order to arrive at a set analogous to the one available for the actinides.
Abstract: Gaussian (14s13p10d8f6g)/[6s6p5d4f3g] atomic natural orbital valence basis sets have been derived for relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety. The existing set of lanthanide pseudopotentials has been supplemented by corresponding potentials for lanthanum and lutetium in order to arrive at a set analogous to the one available for the actinides. Multiconfiguration self-consistent field and subsequent multireference averaged coupled-pair functional calculations are presented for the first to fourth ionization potentials of all lanthanide elements. Molecular calibration studies using the coupled-cluster singles, doubles, and perturbative triples approach are reported for the monohydrides, monoxides, and monofluorides of lanthanum and lutetium.

1,009 citations

Journal ArticleDOI
TL;DR: The aim of this Review is to describe the crucial interaction mechanisms in context, and thus classify the entire subject of supramolecular chemistry.
Abstract: Supramolecular chemistry has expanded dramatically in recent years both in terms of potential applications and in its relevance to analogous biological systems. The formation and function of supramolecular complexes occur through a multiplicity of often difficult to differentiate noncovalent forces. The aim of this Review is to describe the crucial interaction mechanisms in context, and thus classify the entire subject. In most cases, organic host-guest complexes have been selected as examples, but biologically relevant problems are also considered. An understanding and quantification of intermolecular interactions is of importance both for the rational planning of new supramolecular systems, including intelligent materials, as well as for developing new biologically active agents.

968 citations

Journal ArticleDOI
TL;DR: In this article, an effective one-electron spin-orbit Hamiltonian is used, based on atomic mean field integrals, the basic electronic states are obtained using the restricted active space (RAS) SCF method.

910 citations