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Majed Chergui

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Publications associées (250)

Liquid dynamics in ZrO2 nanoporous films

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Time-resolved Optical Kerr Effect (OKE) measurements were used to det. the orientational dynamics of water and acetonitrile in the bulk and in pores of ZrO2 nanostructured films. The expts. were performed with a home-built OKE microscope, capable of provid ...

2007

Femtosecond polarization relaxation in CdSe nanocrystals

Majed Chergui, Frank van Mourik, Awos Al Salman

We present ultrafast pump-probe studies on chem. prepd. CdSe nanocrystals. Upon pulsed optical excitation we find pronounced oscillations, indicating strong coupling to a LO phonon mode. From the polarization dependence of the signal addnl. information abo ...

2007

Ultrafast Nonadiabatic Dynamics of [FeII(bpy)3]2+ in Solution

Majed Chergui, Frank van Mourik, Wojciech Gawelda, Andrea Cannizzo, Van Thai Pham

The ultrafast relaxation of aq. Fe(II)-tris(bipyridine) upon excitation into the singlet metal-to-ligand charge-transfer band (1MLCT) was characterized by femtosecond fluorescence up-conversion and transient absorption (TA) studies. The fluorescence expt. ...

2007

CNDOL: A fast and reliable method for the calculation of electronic properties of very large systems. Applications to retinal binding pocket in rhodopsin and gas phase porphine

Majed Chergui, Ursula Röthlisberger

Very large mol. systems can be calcd. with the so called CNDOL approx. Hamiltonians that have been developed by avoiding oversimplifications and only using a priori parameters and formulas from the simpler NDO methods. A new diagonal monoelectronic term na ...

2007

Structural Determination of a Short-Lived Excited Iron(II) Complex by Picosecond X-Ray Absorption Spectroscopy

Majed Chergui, Wojciech Gawelda, Van Thai Pham

Structural changes of the Fe(II)-tris-bipyridine ([FeII(bpy)3]2+) complex induced by ultrashort pulse excitation and population of its short-lived (?0.6 ns) quintet high spin state were detected by picosecond x-ray absorption spectroscopy. The structural r ...

2007

On the excitation wavelength dependence of the fluorescence of bacteriorhodopsin

Stefan Haacke, Majed Chergui, Selma Schenkl, Erwin Portuondo Campa, Goran Zgrablic

We present a systematic study of the time-integrated fluorescence of native bacteriorhodopsin, as a function of excitation wavelength across the visible absorption band. While the fluorescence max. is unaffected, the spectrum broadens on the high-energy si ...

Elsevier2007

Capturing transient electronic and molecular structures in liquids by picosecond X-ray absorption spectroscopy

Majed Chergui, Wojciech Gawelda, Amal El Nahhas, Van Thai Pham

We describe an advanced setup for time-resolved x-ray absorption fine structure (XAFS) spectroscopy with picosecond temporal resoln. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of th ...

2007

Observation of the Solvent Shell Reorganization around Photoexcited Atomic Solutes by Picosecond X-ray Absorption Spectroscopy

Majed Chergui, Wojciech Gawelda, Van Thai Pham

We report on the observation of the solvation shell rearrangement after abstraction of the electron from aq. I- in a laser pump/X-ray probe expt. by recording the X-ray absorption L1- and L3-edge spectra, 50 ps after laser excitation. The L1-edge spectra c ...

2007

Modelling of aqueous solvation of eosin Y at the rutile TiO2(110)/water interface

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Mol. dynamics simulations at 298 K are used to study an aq. dissolved dye (eosin Y) adsorbed at the TiO2(1 1 0) surface to ext. static and dynamic information of solvation. Differences in the phys. behavior of the dye at the surface and in bulk H2O are com ...

Elsevier2006

Electronic and Molecular Structure of Photoexcited [RuII(bpy)3]2+ Probed by Picosecond X-ray Absorption Spectroscopy

Majed Chergui, Wojciech Gawelda

L2,3 x-ray absorption spectra of aq. [RuII(bpy)3]2+ were recorded in its ground and excited states, 50 ps after short pulse laser excitation. Significant changes in both the XANES (x-ray Near-Edge Absorption Structure) and the EXAFS (Extended x-ray Absorpt ...

2006

Sulfide-binding hemoglobins: effects of mutations on active-site flexibility

Majed Chergui

The dynamics of Hb I (HbI) from the clam Lucina pectinata, from wild-type sperm whale (SW) myoglobin, and from the L29F/H64Q/V68F triple mutant of SW, both unligated and bound to hydrogen sulfide (H2S), have been studied in mol. dynamics simulations. Featu ...

2006

Photexcitation of Aqueous Ruthenium(II)-tris-(2,2'-bipyridine) with High-Intensity Femtosecond Laser Pulses

Majed Chergui, Wojciech Gawelda

The authors report a femtosecond pump-probe study of photochem. of concd. aq. solns. of [Ru(bpy)3]2+, as a function of pump power (up to 2 TW/cm2) at 400 nm excitation. The transient absorption spectra in the 345-660 nm range up to 1 ns time delay enable t ...

2006

Time-Resolved Photodynamics of Triangular-Shaped Silver Nanoplates

Majed Chergui, Frank van Mourik, Luigi Bonacina, Camilla Bonati, Andrea Callegari

The authors measured the ultrafast response of triangular silver nanoparticles upon femtosecond excitation of their plasmon resonance. After a fast electron relaxation, the signature of a bimodal mech. vibration of the particle is apparent as a spectral mo ...

2006

Aqueous Solvation Dynamics at Metal Oxide Surfaces

Jacques-Edouard Moser, Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Broadband transient absorption (TA) spectroscopy, three-pulse photon echo peak shift (3PEPS), and anisotropy decay measurements were used to study the solvation dynamics in bulk water and interfacial water at ZrO2 surfaces, using Eosin Y as a probe. The 3P ...

2006

Controlling Biological Functions

Majed Chergui

A review. Manipulation of the quantum properties of matter can influence the course of biochem. reactions. Can biol. functions, such as vision or photosynthesis, that are driven by incoherent phenomena have anything to do with quantum mechanics, where the ...

American Association for the Advancement of Science2006

Absorption spectroscopy of three-dimensional bacteriorhodopsin crystals at cryogenic temperatures: effects of altered hydration

Majed Chergui, Selma Schenkl, Erwin Portuondo Campa

A comparative study of absorption spectroscopy at 100 K has been performed on three-dimensional crystals of bacteriorhodopsin extd. from a lipidic cubic phase and on native purple membrane. A modified microspectrophotometer has been designed which yields a ...

2006

A Full Multiple Scattering Model for the Analysis of Time-Resolved X-ray Difference Absorption Spectra

Majed Chergui, Wojciech Gawelda

A full multiple theor. model (MXAN) is applied to fit picosecond difference x-ray absorption spectra at the Ru L3 edge upon photoexcitation of aq. [RuII(bpy)3]2+. Fitting difference spectra allows an increase in sensitivity, such that slight structural cha ...

2006

The ultrafast structural response of solid parahydrogen: a complementary experimental/simulation investigation

Majed Chergui, Frank van Mourik, Luigi Bonacina

A complete characterization, based on fs pump-probe spectroscopy and mol. dynamics simulations, is presented of the ultrafast dynamics of electronic bubble formation in solid para-H2 upon impulsive excitation of impurity-doped sites, which correlate with t ...

2006

Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption

Majed Chergui, Selma Schenkl, Frank van Mourik

A visible-pump/UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resoln. We identify three spectral components in the 265- to 310-nm region, related to the all-trans retinal, tryptophan (Trp)- ...

National Academy of Sciences2006

Broadband femtosecond fluorescence spectroscopy of [Ru(bpy)3]2+

Majed Chergui, Frank van Mourik, Wojciech Gawelda, Goran Zgrablic, Andrea Cannizzo

Femtosecond fluorescence-upconversion studies of aq. [Ru(bpy)3]2+ show a short-lived vibrationally hot emission of the singlet metal-to-ligand charge-transfer state, with an ultrafast intersystem crossing (~ 10 fs) to the triplet state at const. energy (th ...

Wiley-VCH Verlag GmbH2006

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