Publications de Majed Chergui | EPFL Graph Search

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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. ...

The computation of stationary optical spectra of mol. systems based on a wavepacket propagation on excited potential energy surfaces (PES) is extended to the condensed phase case in utilizing the d. matrix theory. As an example, a one-dimensional model is studied for the photodissocn. of matrix isolated HCl. Emphasis is put on the interplay of the cage effect and the energy dissipation into the matrix. [on SciFinder (R)]

The coherent Fluorescence Resonance Energy Transfer (FRET) combined with Scanning Near-Field Optical Microscopy (SNOM) are proposed for the creation of complex and nonlocal entangled states involving hundreds of atoms. Micro- and milli-second decoherence times of the electron excitation occur for rare-earth dopant ions in crystals at low temps., and the characteristic coherent FRET distances for such systems are of the order of 20 nm. Thus, both position and time precision necessary for the quantum manipula

Tryptophan is commonly used to study protein structure and dynamics, such as protein folding, as a donor in fluorescence resonant energy transfer (FRET) studies. By using ultra-broadband ultrafast two-dimensional (2D) spectroscopy in the ultraviolet (UV) a ...

The spectrally and temporally resolved fluorescence properties of native bacteriorhodopsin (bR) and bR reconstituted with a nonisomerizing analog of the retinal Schiff base (bR5.12) are examd. The first attempt to exptl. monitor the excited state relaxation processes in both type of pigments using ultrafast fluorescence spectroscopy is reported. The fluorescence is emitted from retinal mols. in an all-trans configuration. Substantial energy relaxation involves very fast intramol. and intermol. vibrational m

We describe an experimental setup, which measures transient chemical changes of photoexcited solutes in disordered systems via time-resolved X-ray Absorption Spectroscopy (XAS) with picosecond temporal resolution. The setup combines a femtosecond amplified ...

Three new progressions consisting of broad bands were obsd. in the absorption spectrum of NO in solid Ar. They are identified as the mol. Rydberg A 2.sum.+,C 2P and D 2.sum.+-X 2P (v', 0) transitions, blue shifted with respect to the gas phase by .apprx.0.85 eV. Excitation of the mol. yields emission from A 2.sum.+ (v = 0) with large absorption-emission Stokes shifts, and from the valence B 2P(v = 0) and a 4P(v = 0) states. Intensity ratios between these states in Ar, Kr, and Xe matrixes are given and discu

The excited state non-adiabatic dynamics of polyatomic molecules, leading to the coupling of structural and electronic dynamics, is a fundamentally important yet challenging problem for both experiment and theory. Ongoing developments in ultrafast extreme ...

Ultrafast X-ray absorption spectroscopy is a powerful tool to observe electronic and geometric structures of short-lived reaction intermediates. The ab initio FEFF9 code is applied to simulate the Pt L-3-edge XANES spectrum of the photocatalytic diplatinum molecule Pt-2(P2O5H2)(4) and the photo-induced changes that occur therein. The spectra are interpreted within a XAFS-like scattering theoretical framework (bound-continuum transitions) or in terms of a final-state local l-projected density of states

Optical-domain transient grating (TG) spectroscopy is the ideal tool to investigate transport phenomena in gases, liquids and solids, but it is limited to typically micron-size grating periods. Extreme-Ultraviolet TG has represented a major leap forward to ...

Dynamical information on spin degrees of freedom of proteins or solids can be obtained by NMR and electron spin resonance. A technique with similar versatility for charge degrees of freedom and their ultrafast correlations could move the understanding of s ...

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 ...

Higher Rydberg states of NO trapped in rare gas matrixes were studied by inducing Rydberg-Rydberg transitions from the lowest A2S+ (3ss) Rydberg state and detecting its fluorescence depletion. This technique unravels Rydberg states, which cannot be accessed by ground state absorption. However, no clear cut Rydberg series show up. The data show a compression of the n-(n + 1) splittings between Rydberg states, and of the ll splittings. The results are rationalized in terms of the quantum defect model and the

A comprehensive microscopic description of thermally induceddistortions in lead halide perovskites is crucial for their realistic applications, yetstill unclear. Here, we quantify the effects of thermal activation in CsPbBr3nanocrystals across length scales with atomic-level precision, and we provide aframework for the description of phase transitions therein, beyond the simplisticpicture of unit-cell symmetry increase upon heating. The temperature increasesignificantly enhances the short-range structural d

New time and energy resolved data on vibrationally relaxed and unrelaxed emissions from the valence a4P(v = 0), B2P(v = 0,3,4,5), and the Rydberg A2S+ (v = 0,1,2) states of NO in Ne matrixes are reported. Rydberg .tautm. valence and valence .tautm. valence nonradiative transitions were identified. The Rydberg -> valence transitions occur after lattice relaxation accommodating the Rydberg orbital. The branching ratios for intramol. relaxation and the measured lifetimes are described in terms of a model which

Excitation of the A(3ss) Rydberg state of NO trapped in an H2 crystal leads to the electronic bubble formation around the NO impurity, resulting in an increase of 0.9 .ANG. of the ground state cage radius. Its dynamics was followed in real-time by femtosecond pump-probe spectroscopy. Bubble formation is completed in .apprx.1.5 ps without recurrences of the cage motion. A model based on classical hydrodynamics provides quant. agreement with exptl. data, suggesting that solid H can be described like a liq. on

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 ...

After presenting the basic theoretical models of excitation energy transfer and charge transfer, I describe some of the novel experimental methods used to probe them. Finally, I discuss recent results concerning ultrafast energy and charge transfer in biol ...

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 ...

Majed Chergui

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

Density matrix propagation and stationary absorption spectra: HCl in rare gas matrixes

Coherent fluorescence resonance energy transfer: Construction of nonlocal multiparticle entangled states and quantum computing

Ultrafast Tryptophan-to-Heme Electron Transfer in Myoglobins Revealed by UV 2D Spectroscopy

Femtosecond and picosecond fluorescence of native bacteriorhodopsin and a nonisomerizing analog

Picosecond time-resolved X-ray Absorption Spectroscopy of solvated organometallic complexes

Rydberg states and intramolecular relaxation of nitric oxide trapped in rare gas matrixes

Beyond structure: ultrafast X-ray absorption spectroscopy as a probe of non-adiabatic wavepacket dynamics

L-edge XANES analysis of photoexcited metal complexes in solution

Launching Structural Dynamics

All Hard X-ray Transient Grating Spectroscopy

Coupling of a high-energy excitation to superconducting quasiparticles in a cuprate from coherent charge fluctuation spectroscopy

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

Rydberg states in the condensed phase studied by fluorescence depletion spectroscopy

Atomic-Level Description of Thermal Fluctuations in Inorganic LeadHalide Perovskites

Electronic and vibrational relaxation in Rydberg and valence states of nitric oxide in neon matrixes

Dynamics of electronic "bubble" formation in solid hydrogen

Liquid dynamics in ZrO2 nanoporous films

Ultrafast photoinduced energy and charge transfer

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