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Majed Chergui

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Publications associées (250)

Photon echo peak shift experiments in the UV: p-terphenyl in different solvents

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

We present a new photon echo set-up operating in the UV range and our 1st results of photon echo peak shift (PEPS) expts. of a small non-polar dye mol., p-terphenyl (pTP), in 3 different solvents: EtOH, MeOH, and 2-propanol. The expts. show the feasibility ...

2008

EXAFS structural determination of the Pt2(P2O5H2)44- anion in solution

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

We present the first structural detn. of the Pt2(P2O5H2)44- anion in soln. by analyzing the extended X-ray absorption fine structure (EXAFS) spectrum of the Pt LIII edge. The data could be fit with a simple model involving single and multiple scattering pa ...

2008

Linear dichroism of CdSe nanodots: Large anisotropy of the band-gap absorption induced by ground-state dipole moments

Majed Chergui, Frank van Mourik

The authors measured the elec. field induced linear dichroism for a wide range of sizes of CdSe nanocrystals. Large ground-state dipole moments were obsd., esp. for the smallest crystals. In these, the authors found a very large anisotropy of the absorptio ...

2008

Direct Observation of Microscopic Solvation at the Surface of Clusters by Ultrafast Photoelectron Imaging

Majed Chergui, Alejandro Gonzalez Gonzalez

We report on microscopic observation of solvation by argon atoms of excited states of an ethylenic-like mol., TDMAE (tetrakis dimethylaminoethylene). Two exptl. methods were used: gas phase dynamics for the observation of the evolution through excited stat ...

2008

Ultrafast nonresonant response of TiO2 nanostructured films

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

The authors present a detailed study of the nonresonant 3rd-order ultrafast response of TiO2 nanostructured films, combining a classical heterodyned optical Kerr effect expt., with 2 polarization selective Kerr techniques, based on transient lensing and ph ...

2008

Exploiting EXAFS and XANES for time-resolved molecular structures in liquids

Majed Chergui

A review. Time-resolved X-ray absorption fine structure (XAFS) spectroscopy with picosecond temporal resoln. is a new method to observe electronic and geometric structures of short-lived reaction intermediates. It combines an intense femtosecond laser sour ...

2008

Optical Kerr effect studies of the dynamics of confined water

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Time resolved optical Kerr effect measurements have been used to det. the orientational dynamics of water in the pores of ZrO2 nanostructured films. We demonstrate that local heating effects can safely be ignored and present our results which are manifestl ...

2008

A simple and accurate method for calibrating the oscillation amplitude of tuning-fork based AFM sensors

Majed Chergui, Jinquan Liu, Andrea Callegari

We have developed a simple and accurate method for calibrating the amplitude of vibration of quartz tuning fork sensors commonly used in at. force- and near field optical-microscopy. Unlike interferometric methods, which require a complex optical setup, th ...

2008

Multimodal Distribution of Quantum Confinement in Ripened CdSe Nanocrystals

Majed Chergui, Awos Al Salman, Philip Pattison

We present three different prepn. methods for CdSe colloidal nanoparticles that, when carried out into the Ostwald ripening regime, lead to the development of complex spectral patterns resulting from the overlap of several distinct components corresponding ...

2008

Femtosecond Fluorescence and Intersystem Crossing in Rhenium(I) Carbonyl-Bipyridine Complexes

Majed Chergui, Amal El Nahhas, Andrea Cannizzo

Ultrafast electronic-vibrational relaxation upon excitation of the singlet charge-transfer b1A' state of [Re(L)(CO)3(bpy)]n (L = Cl, Br, I, n = 0; L = 4-Et-pyridine, n = 1+) in acetonitrile was investigated using the femtosecond fluorescence up-conversion ...

2008

Ultrafast UV photon echo peak shift and fluorescence up conversion studies of non-polar solvation dynamics

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

The authors present photon echo peak shift and femtosecond fluorescence up-conversion studies of nonpolar solvation dynamics of a simple nonpolar dye p-terphenyl in EtOH and cyclohexane, using excitation in the UV range at 290 nm. The UV fluorescence up-co ...

2008

Relaxation processes of point defects in vitreous silica from femtosecond to nanoseconds

Majed Chergui, Frank van Mourik, Wojciech Gawelda, Erwin Portuondo Campa, Andrea Cannizzo, Andrea Callegari

The authors studied ultrafast relaxation of localized excited states at Ge-related O deficient centers in SiO2 using femtosecond transient-absorption spectroscopy. The relaxation dynamics exhibits a biexponential decay, which the authors ascribe to the dep ...

2008

An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds

Stefan Haacke, Majed Chergui, Andrea Cannizzo

Single mols. that act as light-energy transducers (e.g., converting the energy of a photon into at.-level mech. motion) are examples of minimal mol. devices. Here, we focus on a mol. switch designed by merging a conformationally locked diarylidene skeleton ...

National Academy of Sciences2008

Time-resolved X-ray absorption spectroscopy

Majed Chergui

Changes in electronic structure are the source of structural modifications in photochem. and photobiol. processes, occurring at ultrafast time scales (between femto- and picosecond times). An original method to probe these changes based upon a pump probe m ...

2008

Subpicosecond near-infrared fluorescence upconversion study of relaxation processes in PbSe quantum dots

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

The (sub)-ps relaxation processes in PbSe quantum dots of different sizes were measured by near-IR luminescence upconversion. The early-time spectra are characterized by emission from several low-lying excited states. The direct measurement of the Huang-Rh ...

2007

Cellular photoperception and photoactive proteins

Stefan Haacke, Majed Chergui

A review. The crucial steps of cellular photoperception are characterized and followed in real time by laser spectroscopy down to a few tens of femtoseconds. The photoactive proteins studied here are involved in major natural processes such as vision (bact ...

2007

Temperature effects on the spectral properties of colloidal CdSe nanodots, nanorods, and tetrapods

Majed Chergui, Frank van Mourik, Awos Al Salman

The temp. dependence of the absorption and fluorescence spectra of colloidal CdSe nanocrystals was compared for three different shapes (dots, rods, and tetrapods) at 4-300 K. While the shift of the fluorescence max. indicates little dependence on the shape ...

2007

Femtosecond fluorescence upconversion setup with broadband detection in the ultraviolet

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

We show a femtosecond fluorescence upconversion setup with broadband detection to measure time-resolved emission spectra in the 300-550 nm range, upon excitation between 250 and 300 nm, with a time resolution of 100 fs. We present time-resolved fluorescenc ...

2007

Light-induced spin crossover probed by ultrafast optical and X-ray spectroscopies

Majed Chergui, Wojciech Gawelda, Amal El Nahhas, Andrea Cannizzo, Van Thai Pham, Renske Marjan van der Veen

The photoinduced energy and structural relaxation of aq. iron(II)-tris-bipyridine ([FeII(bpy)3]2+), upon excitation into its singlet metal-to-ligand charge transfer (1MLCT) band, and the population of its short-lived (?0.6 ns) high-spin excited state have ...

2007

Vibrational coherences of the protonated Schiff base of all-trans-retinal in solution

Stefan Haacke, Majed Chergui, Goran Zgrablic

Modulations in the time gated ultrafast fluorescence of the protonated Schiff base of retinal in various solvents are reported, which reflect the creation and evolution of vibrational wave packets due to the torsional mode of retinal of frequency .apprx.12 ...

2007

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