Publications de Majed Chergui | EPFL Graph Search

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We report UV and visible mol. ion-pair emission upon 193 nm excitation of I2 in solid xenon. By comparison to mol. emission obsd. in Kr matrixes, it is assigned to the d(2u)->2g (I*+I) and d(2u)->2g (I+I) transitions. The solvation energy of this charge transfer state is surprisingly small, and the fluorescence is efficiently quenched when the sample temp. is raised. Population may partially flow into valence states correlating to the I*+I* asymptotes. In contrast to all lighter matrixes, I*+I*->I2 luminesc

Rydberg series obsd. in the excitation spectra of Cl and H atoms isolated in the rare gas (Rg) crystals Kr and Xe are assocd. with the charge transfer species Cl-Rg+ and H-Rg+. The progressions originate from hole states of Rg+ which converge to the top of the rare gas valence band in an analogous manner to the convergence of conventional exciton states to the bottom of the conduction band. A model based on the effective mass approxn. and a quantum defect concept predicted such progressions in Xe and Kr cry

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 ...

The advent of ultrafast laser spectroscopy has allowed entirely new possibilities for the investigation of the ultrafast photophysics of inorganic metal-based molecular complexes. In this review we show different regimes where non-Kasha behavior shows up. ...

We present an ab initio Born-Oppenheimer molecular dynamics study of the early time solvent dynamics after electron abstraction from aqueous iodide. An initial response occurs within ∼75 fs, corresponding to a water molecule sharing almost one electron wit ...

Self-diffraction is a four-wave mixing process proportional to the square modulus of third-order nonlinearity susceptibility χ (3) , which is related to the material’s electronic and thermal properties. In this study, we investigate the wavelength dependence of the self-diffracted signal generated by a femtosecond pulsed laser in a dye solution to directly evaluate the electronic third-order nonlinear susceptibility spectrum. By accounting for absorption effects and phase matching conditions, we determine t

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 ...

Wavelength- and time-resolved fluorescence expts. have been performed on the photoactive yellow protein, the E46Q mutant, the hybrids of these proteins contg. a nonisomerizing "locked" chromophore, and the native and locked chromophores in aq. soln. The ultrafast dynamics of these six systems is compared and spectral signatures of isomerization and solvation are discussed. We find that the ultrafast red-shifting of fluorescence is assocd. mostly with solvation dynamics, whereas isomerization manifests its

The manipulation of the electronic properties of solids by light is an exciting goal, which requires knowledge of the electronic structure with energy, momentum and temporal resolution. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) is the ...

The collisional energy dependence of the cross section for the Penning ionization of C60 mols. by metastable neon atoms was measured in the 0.035-0.5 eV range in a crossed beam expt. The results show a decreasing trend (.apprx.20%) in the low-energy range up to 0.06 eV, with a slightly increasing dependence in the higher energy range. This behavior is interpreted in terms of the characteristics of the intermol. interaction: an electron transfer can be possible from the metastable rare gas atom to the C60 mo

Absorption, fluorescence and excitation spectra of three-dimensional bacteriorhodopsin crystals harvested from a lipidic cubic phase are presented. The combination of the spectroscopic expts. performed at room temp., controlled pH and full external hydration reveals the presence of three distinct protein species. Besides the well-known form obsd. in purple membrane, we find two other species with a relative contribution of up to 30%. As the spectra are similar to those of dehydrated or deionized membranes c

Controlling the temporal and kinetic statistics of excitons in semiconductor nanocrystals is important for understanding how multiexcitonic processes emerge in ultrafast excited‐state dynamics under low‐fluence conditions. Under conventional single‐pulse excitation, the Poissonian nature of exciton generation limits the manifestation of biexciton‐mediated processes in the observed kinetics at low fluence. Here, we demonstrate a sequential ultrafast excitation scheme in CsPbBr 3 nanocrystals that reshapes th

Transition metal oxides are among the most promising solar materials, whose properties rely on the generation, transport and trapping of charge carriers (electrons and holes). Identifying the latter's dynamics at room temperature requires tools that combin ...

We report on a study of the early relaxation processes of met-Myoglobin in aqueous solution, using a combination of ultrafast broadband fluorescence detection and transient absorption with a broad UV-visible continuum probe at different pump energies. Reco ...

The measurement of chirality and its temporal evolution are crucial for the understanding of a large range of biological functions and chemical reactions. Steady-state circular dichroism (CD) is a standard analytical tool for measuring chirality in chemist ...

Studies of the electronic transitions of the n = 1 (1P1, 3P1 - 1S0) exciton in solid rare gases at different vols. can yield valuable information about intermol. potentials. A computer calcn. of the absorption and emission energies of solid Ne was performed; the effect of pressure shifts the lines to higher energies. The results at zero pressure stress the importance of zero point motion in a Ne crystals and the need for improved potential curves. [on SciFinder (R)]

Controlling the ultrafast photodynamics of metal-free organic molecules has great potential for technological applications. In this work, we use solvent polarity and viscosity as "external knobs" to govern the photodynamics of an electron-donating derivati ...

Femto- to picosecond excited-state dynamics of the complexes Re(L)(CO)(3)(N,N) (N,N = bpy, phen, 4,7-dimethyl-phen (dmp); L = Cl, n = 0; L = imidazole, n = 1+) were investigated using fluorescence up-conversion, transient absorption in the 650-285 nm ...

Electronic and vibrational relaxationsof NO in Ar, Kr, and Xe matrixes were studied using excitation spectra and time and energy resolved emission spectra. In addn. to the vibrationally relaxed emissions from a4P(v = 0), B 2P(v = 0), and A 2S+ (v = 0) in Ar and Kr matrixes, B(v = 5 and 7) emissions were obsd. in Ar matrixes. In Xe matrixes, only Rydberg A 2S+ (v = 0) fluorescence is obsd. Nonradiative Rydberg-valence transitions are obsd. in all matrixes and valence-Rydberg transitions only in Ar matrixes.

Several new progressions consisting of broadbands were obsd. in the absorption spectra of NO trapped in rare gas matrixes. They were identified as the blue shifted transitions to the n = 3 (A 2S+, C 2P, D 2S+) and n = 4 (E 2S+, K 2P, M 2S+) Rydberg states of NO in Ne matrixes and to the n = 3 Rydberg states in Ar, Kr, and Xe matrixes. Linewidths (50 to 180 meV) and matrix shifts (0.3 to 1.2 eV) decrease from Ne to Xe matrixes. For each matrix, the shifts decrease according to the symmetry of the excited sta

Majed Chergui

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Luminescence of ion-pair and spin-excited states of I2 in solid xenon

Rydberg series of charge-transfer excitations: atomic chlorine and atomic hydrogen in rare gas crystals

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

Empirical rules of molecular photophysics in the light of ultrafast spectroscopy

Solvent rearrangements during the transition from hydrophilic to hydrophobic solvation

Femtosecond self-diffraction as a measure of the nonlinear response spectrum

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

Contrasting the excited-state dynamics of the photoactive yellow protein chromophore: Protein versus solvent environments

Time-resolved ARPES at LACUS: Band Structure and Ultrafast Electron Dynamics of Solids

Dynamics of the Penning Ionization of Fullerene Molecules by Metastable Neon Atoms

Compositional Heterogeneity Reflects Partial Dehydration in Three-dimensional Crystals of Bacteriorhodopsin

Enhanced Contribution of Biexciton‐Mediated Decay Kinetics in Perovskite Nanocrystals Via Sequential Ultrafast Excitation

Femtosecond X-ray absorption study of electron localization in photoexcited anatase TiO2

A cascade through spin states in the ultrafast haem relaxation of met-myoglobin

Ultrafast broadband circular dichroism in the deep ultraviolet

Pressure effects on the absorption and emission of the n = 1 exciton in solid neon

Early bird or night owl? Controlling the ultrafast photodynamics of triphenylamine substituted 2,2′:6′,2′′-terpyridine

Ultrafast Excited-State Dynamics of Rhenium(I) Photosensitizers [Re(Cl)(CO)(3)(N,N)] and [Re(imidazole)(CO)(3)(N,N)](+): Diimine Effects

Nonradiative Rydberg .tautm. valence relaxation of nitric oxide trapped in argon, krypton, and xenon matrixes

Rydberg states of nitric oxide trapped in rare gas matrixes