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Majed Chergui

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Publications associées (250)

RETRACTED: Charge transfer to solvent identified using dark channel fluorescence-yield L-edge spectroscopy

Majed Chergui, Mercedes Hannelore Rittmann-Frank

Aqueous ions are central to catalysis and biological function and play an important role in radiation biology as sources of damage-inducing electrons. Detailed knowledge of solute-solvent interactions is therefore crucial. For transition-metal ions, soft X ...

2010

Electron Localization Dynamics in the Triplet Excited State of Ru(bpy)3]2+ in Aqueous Solution

Majed Chergui, Marc-Etienne Moret, Ursula Röthlisberger, Ivano Tavernelli

Hybrid DFT/classical molecular dynamics of the long-lived triplet excited state of [Ru(bpy)3]2+ (bpy=2,2-bipyridine) in aqueous solution is used to investigate the solvent-mediated electron localization and dynamics in the triplet metal-to-ligand charge-tr ...

2010

Picosecond and femtosecond X-ray absorption spectroscopy of molecular systems

Majed Chergui

The need to visualize molecular structure in the course of a chemical reaction, a phase transformation or a biological function has been a dream of scientists for decades. The development of time-resolved X-ray and electron-based methods is making this tru ...

2010

RETRACTED: On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre

Majed Chergui

Catalase and methaemoglobin have very similar haem groups, which are both ferric, yet catalase decomposes hydrogen peroxide to water and oxygen very efficiently, while methaemoglobin does not. Structural studies have attributed this behaviour to their diff ...

Royal Society of Chemistry2010

Electron and X-ray methods of ultrafast structural dynamics: advances and applications

Majed Chergui

A review. The state of the art in the detn. of structures with ultrafast electrons and x-rays is highlighted. Perspectives and reflections on the principles, techniques, and methods are provided, and on applications from different disciplines, with some fo ...

2009

Heterogeneity and relaxation dynamics of the photoexcited retianl Schiff base cation in solution

Stefan Haacke, Majed Chergui, Goran Zgrablic

We present steady-state and broadband femtosecond fluorescence spectra of the protonated Schiff base of retinal in various protic and aprotic solvents, as a function of the excitation wavelength. A detailed spectral decomposition of the time-resolved fluor ...

2009

Time-resolved x-ray absorption spectroscopy: Watching atoms dance

Majed Chergui, Paul Beaud, Wojciech Gawelda, Camelia Borca, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

The introduction of pump-probe techniques to the field of x-ray absorption spectroscopy (XAS) has allowed the monitoring of both structural and electronic dynamics of disordered systems in the condensed phase with unprecedented accuracy, both in time and i ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2009

Structural analysis of ultrafast extended x-ray absorption fine structure with subpicometer spatial resolution : Application to spin crossover complexes

Majed Chergui, Wojciech Gawelda, Van Thai Pham, Renske Marjan van der Veen

We present a novel analysis of time-resolved extended x-ray absorption fine structure (EXAFS) spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments. We apply it to the analysis of picosecond EXAFS da ...

2009

Probing the Electronic Structure of the Hemoglobin Active Center in Physiological Solutions

Majed Chergui

Soft-x-ray absorption spectroscopy at the L2,3 edge of the iron center in bovine Hb and hemin under physiol. conditions is reported for the first time. Spectra of the same compds. in solid form are presented for comparison. Striking differences in the elec ...

2009

Vibrational coherences and relaxation in the high-spin state of aqueous [Fell(bpy)3]2+

Majed Chergui, Frank van Mourik, Amal El Nahhas, Andrea Cannizzo, Mirabelle Prémont-Schwarz, Cristina Consani

Dizzy cooling: Femtosecond excitation of the singlet states of aqueous [FeII(bpy)3]2+ (bpy=2,2-bipyridine) leads to the formation of a vibrationally hot quintet state that exhibits wave-packet dynamics arising from a chelate-ring and bending mode. The vibr ...

Wiley-VCH Verlag GmbH2009

Structural determination of photochemically active diplatinum molecule by time-resolved EXAFS spectroscopy

Majed Chergui, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

Metallica: A large contraction of the PtPt bond in the triplet excited state of the photoreactive [Pt2(P2O5H2)4]4- ion is determined by time-resolved X-ray absorption spectroscopy (see picture). The strengthening of the PtPt interaction is accompanied by a ...

Wiley-VCH Verlag GmbH2009

Femtosecond XANES Study of the Light-Induced Spin Crossover Dynamics in an Iron(II) Complex

Majed Chergui, Paul Beaud, Wojciech Gawelda, Camelia Borca, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen

X-ray absorption spectroscopy is a powerful probe of mol. structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aq. iron(II) tris(bipyridi ...

American Association for the Advancement of Science2009

Functional electric field changes in photoactivated proteins revealed by ultrafast Stark spectroscopy of the Trp residues

Stefan Haacke, Majed Chergui, Frank van Mourik, Erwin Portuondo Campa, Andrea Cannizzo

Ultrafast transient absorption spectroscopy of wild-type bacteriorhodopsin (WT bR) and 2 tryptophan mutants (W86F and W182F) is performed with visible light excitation (pump) and UV probe. The aim is to investigate the photoinduced change in the charge dis ...

2009

The molecular cat

Majed Chergui

A manifestation of electronic entanglement in core-level spectroscopic measurements of diatomic molecules, reported recently by Schoffler and co-workers, is discussed. The results are reminiscent of Schrodinger's famous Gedanken experiment with the cat (se ...

2009

A model for the multi-exponential excited-state decay of CdSe nanocrystals

Majed Chergui, Frank van Mourik, Awos Al Salman

We report on photoluminescence decay measurements of CdSe nanoparticles over several decades of intensities and times, and as a function of size and temp. A model is proposed for the multi-exponential decay kinetics, and their temp. dependence, in which a ...

2009

Broadband femtosecond fluorescence up-conversion and photon echo experiments in the UV

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei

The fs-time-resolved study of a small UV dye in different solvents with fluorescence up-conversion and photon-echo techniques in the UV range provides new insight in cooling relaxation and solvation dynamics of non-polar molecules in polar solvents. ...

Springer-Verlag New York, Ms Ingrid Cunningham, 175 Fifth Ave, New York, Ny 10010 Usa2009

Retrieving photochemically active structures by time-resolved EXAFS spectroscopy

Majed Chergui, Wojciech Gawelda, Camelia Borca, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

Describing the nature and structure of molecular excited states is important in order to understand their chemical reactivity and role as intermediates in photochemical reactions. The recent implementation of x-ray absorption spectroscopy in the ultrafast ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2009

Calculation of surface Plasmon frequencies of two, three and four strongly interacting nanospheres

Majed Chergui

An approximate analytical approach is developed for the calculation of the surface plasmon frequency of a system of interacting nanospheres for arbitrary values of interparticle distances. In addition to having a simple and physically clear form, the final ...

2009

Ultrarapid Reaction in Solution - Experimental and Theoritical - Approaches by Mehran Mostafavi and Thomas Gustavsson

Majed Chergui

2008

Sub-picosecond polychromatic photoluminescence studies of CdSe and PbSe nanodots

Majed Chergui, Frank van Mourik, Camilla Bonati, Andrea Cannizzo

We present our studies of femtosecond photoluminescence of colloidal solns. of CdSe and PbSe nanocrystals, using polychromatic fluorescence upconversion. Ultrafast relaxation processes are obsd. in both cases upon excitation at 400 nm and 800 nm resp. Unde ...

2008

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