Publications de Majed Chergui | EPFL Graph Search

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The study of oxygen-sensitive biological samples requires an effective control of the atmosphere in which they are housed. In this aim however, no commercial anaerobic chamber is adequate to solely enclose the sample and small enough to fit in a compact sp ...

Dissocn. efficiencies for excitation of the repulsive A 1P state of HCl were recorded in Xe, Kr, and Ar matrixes for photon energies between 5 and 10 eV from the content of dissocn. products and quantum efficiencies were derived with the absorption spectra. Influence of temp. and prepn. conditions was investigated. The quantum efficiency rises monotonically in Xe from an excess energy of 1.4 eV above the gas phase dissocn. energy on, sats. around 2.4 eV and remains then essentially const. up to 4 eV. In Ar

Highly homogeneous and luminescent CdSe colloidal nanocrystals in the less common zinc blende crystal structure have been obtained at high temperature in a noncoordinating organic solvent. The key parameter appears to be the addition of a phosphonic acid t ...

The dye coumarin 343 (C343) adsorbed on the surface of ZrO2 nanoparticles in aq. solns. was used to study the solvation dynamics close to these surfaces. The time-resolved Stokes shift was measured by femtosecond frequency-resolved upconversion. The absorption and fluorescence spectra of C343 in water and adsorbed on ZrO2 were analyzed. The solvation functions of C343 in water and adsorbed on ZrO2 nanoparticles were detd. [on SciFinder (R)]

Chirality in tellurium arises from a Peierls distortion driven by strong electron-phonon coupling, making this material a unique candidate for observing a light-induced topological phase transition. Using time- and angle-resolved photoelectron spectroscopy ...

Recent work on the spectroscopic and photophys. properties of the excited states of Cl2 trapped in an Ar matrix is compared with independent gas-phase results on Cl2 + rare gas as well as with other matrix studies. An alternative interpretation of the results is proposed. [on SciFinder (R)]

In the landscape of ultrafast spectroscopic tools, the deep- and near-ultraviolet ranges (200–400 nm) have lagged behind due to the lack of tunability of both the pump and the probe pulses in this range. With the advent of novel nonlinear optical methods, ...

The optical bandgap of anatase TiO2 nanoparticles is dominated by bulk absorption bands in the deep-ultraviolet due to strongly bound excitons. These spectral features can be utilized as a sensitive probe of carrier and lattice dynamics inside the TiO2 nan ...

We calc. the effects of relatively strong elec. fields, corresponding to typical values for the fields inside glasses and proteins, on the spectroscopic properties of a simple two-level mol. Disorder in the elec. field strength is employed as a phys. source for inhomogeneous broadening. A striking result is that a Gaussian probability distribution for the field over the ensemble does not give rise to a Gaussian spectral line shape. The results are used to describe the absorption spectra of the B800 band of

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 ...

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 ...

Capturing the evolving geometric and electronic structure in the course of a chemical reaction or biological process is the principal aim of time-resolved X-ray spectroscopies. Recent technological and methodological improvements, such as high repetition r ...

A review is presented concerning the exploitation of spectral information carried by probe pulse. The method reviewed allow observing changes and dynamics of the solute mol. structure in polar solvents.

The authors used light to transform a colloidal soln. of spherical silver nanoparticles into larger nanoparticles of a different shape. The particle size and shape can be controlled by choosing the wavelength(s) of light used to drive the photochem. growth. These findings suggest a new way of thinking about growth of nanoparticles in soln. and show the exciting possibility that light can be used as a major control parameter in metallic nanoparticle growth reactions. [on SciFinder (R)]

A red wing in the absorption of H2O in the 1st continuum which extends beyond 200 nm was induced by the matrix. A threshold energy of 6.95 eV was found for the quantum efficiency of permanent dissocn. of H2O into OH and H. This corresponds to an addnl. barrier of 1.8 eV due to the matrix cage. The barrier was attributed to the sum of repulsive H-Ar pair potentials in an interstitial site of D3 symmetry, which must be surmounted by the H atom on the way from the initial substitutional H2O site to the final s

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 ...

Studies of the energy and time-resolved fluorescence of NO D2S+ (v = 0) perturbed by inert gas partners (He, Ne, Ar, Kr and Xe) at various pressures were performed by means of synchrotron radiation. With all rare gases, the collision-induced D (v = 0) -> C (v = 0) cascade was obsd. Depopulation cross sections of D (v = 0) by rare gases were derived which are close to the gas kinetic value. The cross sections for Ne, Ar, Kr and Xe fit C. S. Parmenter et al. (1979) correlation in a satisfactory way. NO (D2S+

The phosphorescence of C60 in Kr and Xe matrixes is reported. It consists of a progression of bands of monotonically decreasing intensity which belong to the hg(1) mode but in Xe weaker contributions from the t1u, t2u, hu and gu modes are also present. In Xe matrixes, the phosphorescence stems from a distribution of sites extending up to 150 cm-1 to the red of the main and most prominent one having its origin at 12714 cm-1. The phosphorescence lifetime is 16 +- 1 ms in Xe and 60 +- 5 ms in Kr. The phosphore

Three new progressions consisting of broad bands (full width at half max. .simeq. 130 meV) were obsd. in the absorption spectrum of NO trapped in an Ar matrix. A Wannier model fails to describe these transitions; they are identified as the mol. Rydberg transitions A2S+, C2P, and D2S+-X2P(v',0), blue shifted with respect to their gas-phase positions by .apprx.0.85 eV. [on SciFinder (R)]

Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional ...

Majed Chergui

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Note: Small anaerobic chamber for optical spectroscopy

Cage exit probability versus excess energy in the photodissociation of matrix-isolated HCl

Synthesis of high quality zinc blende CdSe nanocrystals

Solvation dynamics at water-ZrO2 interfaces

Light-induced renormalization of the band structure of chiral tellurium

An alternative interpretation of the spectroscopy and internal dynamics of excited Cl2 molecules trapped in an argon matrix

Ultrafast molecular photophysics in the deep-ultraviolet

Electron Dynamics in Anatase TiO2 Nanoparticles by Ultrafast Broadband Deep-Ultraviolet Spectroscopy

The Occurrence of Non-Gaussian Spectral Line Shapes of Molecules in Electrostatically Disordered Media

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

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

Recent experimental and theoretical developments in time-resolved X-ray spectroscopies

Observing molecular structure changes and dynamics in polar solution

Photochemically Grown Silver Nanoparticles with Wavelength-Controlled Size and Shape

Cage effect for the abstraction of atomic hydrogen from water in argon matrixes

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

Nitric oxide D2S+ fluorescence quenching by rare gas atoms and van der Waals well depths

Phosphorescence of C60 in rare gas matrixes

Observation of the Rydberg states of nitric oxide trapped in an argon matrix

Radial Spin Texture of the Weyl Fermions in Chiral Tellurium