Publications by Majed Chergui | EPFL Graph Search

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The photochem. of ICN isolated in Ar matrixes has been investigated using UV absorption and laser spectroscopy under a variety of exptl. conditions. Laser excitation of the repulsive ~A continuum gives rise to long-lived near-IR emission from stabilized I and CN fragments in the shallow excited 3P2 potential and to the formation of the INC isomer. The latter is identified by its UV absorption band, which overlaps the ICN UV absorption. A photoinduced equil. is rapidly established between the two species und

Accurate detn. of the transient electronic structures, which drive photochem. reactions, is crucial in chem. and biol. The authors report the detection of transient chem. changes on the picosecond time scale by x-ray-absorption near-edge structure of photoexcited aq. [Ru(bpy)3]2+. Upon ultrashort laser pulse excitation a charge transfer excited state having a 300 ns lifetime is formed. The authors detect the change of oxidn. state of the central Ru atom at its L3 and L2 edges, at a temporal resoln. of 100 p

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 ...

Elucidating the details of electron-phonon coupling in semiconductors and insulators is a topic of pivotal interest, as it governs the transport mechanisms and is responsible for various phenomena such as spectral-weight transfers to phonon sidebands and s ...

A new UV band system identified as emission from the theor. predicted but so far unobserved 2F state of NO trapped in an Ar matrix is reported. The energy of the v = 0 level is estd. to be 6.57 +- 0.015 or 6.785 +- 0.015 eV. The intensity distribution yields an internuclear distance of 1.415 +- 0.015 .ANG.. [on SciFinder (R)]

The fluorescence resonance energy-transfer (FRET) process was studied between donor dye mols. deposited on the sample surface and acceptor dye mols. deposited on the tips of scanning near-field and at. force microscopes. The FRET process was obsd. only when the tip acquired contact with the sample and took place in regions of sizes of only a few tens of nanometers with only a few thousands (or even hundreds) of mols. involved. The dependence of the FRET intensity on the tip-sample acting force is recorded a

The inter-site transition dynamics in a 2D honeycomb lattice of the Mott-insulator Li2irO3 was investigated via broadband time-resolved spectroscopy. Through two excitation regime corresponding to charger transfer (3.1eV) and across Mott-gap excitation (0. ...

The absorption spectrum of C60 embedded in Ne matrixes in the 410-360 nm region is revisited. A complete assignment of the absorption lines therein is proposed in terms of transition to the ungerade states 1 1G1u, 1 1T1u and 2 1T1u states, with progression of Jahn-Teller hg modes and of the totally sym. ag modes. The authors also identify a new progression at l ? 375 nm, which the authors attribute to the transition to the 2 1T2u state and its hg and gg Jahn-Teller modes. Its pure electronic origin is at .a

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 ...

We discuss our recently reported femtosecond (fs) X-ray emission spectroscopy results on the ligand dissociation and recombination in nitrosylmyoglobin (MbNO) in the context of previous studies on ferrous haem proteins. We also present a preliminary accoun ...

: We report femtosecond Fe K-edge absorption (XAS) and nonresonant X-ray emission (XES) spectra of ferric cytochrome C (Cyt c) upon excitation of the haem (>300 nm) or mixed excitation of the haem and tryptophan (

A threshold near 6.8 eV is obsd. for the dissocn. of H2O (and D2O) via the repulsive A(1B1) potential in rare gas matrixes. The threshold varies within 0.2 eV for exchange of Kr with Ar matrix, upon deuteration, and with temp. The observations are consistent with a prompt dissocn. across matrix-induced barriers of about 1.8 eV caused by the repulsive H-rare gas potentials. The increase of dissocn. efficiency above threshold and its variation with matrix and isotope substitution seen in the expts. is rationa

Fluorescence resonance energy transfer (FRET) was obsd. between donor dye mols. deposited onto the sample surface and acceptor dye mols. deposited onto the scanning near-field optical microscope (SNOM) or at. force microscope tip. FRET was obsd. only when the tip acquired a contact with the sample and took place in a region of few tens of square nanometers in size when thousands (hundreds) of mols. are involved. In view of the obtained results, the perspectives for the construction of a 1-atom FRET SNOM are

We report on the ultrafast dynamics of electronic bubble formation following excitation of the A 3ss Rydberg state of the NO mol. trapped in argon and hydrogen matrixes. The study is carried out by femtosecond fluorescence depletion expts. Apparently in hydrogen, relaxation occurs in .apprx.1.5 ps via a collective displacement of the cage species with no recurrencies. In argon, the cage expands by undergoing coherent recurrencies for over .apprx.3 ps, on its way to the fully relaxed bubble configuration. [o

We report on the electronic dephasing times of the nonpolar chromophore diphenylacetylene (DPA) in ethanol and in cyclohexane (polar and nonpolar solvents respectively) by photon echo measurements in the ultraviolet. Contrary to previous reports, we observed sub-100-fs electronic dephasing times for DPA in both solvents. We identify fast dynamics of tau=40 +/- 10 fs on the photon echo peak shift (PEPS) traces of DPA in ethanol. In addition, we observed a dependence of the PEPS asymptotic value on the tempor

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 ...

Excimer densities of 5 * 1018 cm-3 and a light output of 107 W at 172, 145, and 128 nm were obtained from electron beam excited rare gas crystals. [on SciFinder (R)]

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 ...

The ultrafast dynamics are reported of bubble formation following excitation of the A 2S+ 3ss(v = 0) Rydberg state of NO trapped in Ar matrixes. The study is carried out by a fs pump-probe technique. The detected signal is the depletion of Rydberg fluorescence induced by Rydberg-Rydberg transitions. Possibly the bubble is formed on a timescale of a few ps. [on SciFinder (R)]

Majed Chergui

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Spectroscopy and Photoinduced Dynamics of ICN and Its Photoproducts in Solid Argon

Observing Photochemical Transients by Ultrafast X-Ray Absorption Spectroscopy

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

Anomalous anisotropic exciton temperature dependence in rutile TiO2

A new band system in the ultraviolet emission spectrum of nitric oxide trapped in an argon matrix

Towards the fluorescence resonance energy transfer (FRET) scanning near-field optical microscopy: Investigation of nanolocal FRET processes and FRET probe microscope

Non-equilibrium Inter-site Dynamics of Photoexcited Kitaev α-Li2IrO3

Assignment of the near-UV absorption spectrum of C60

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

Femtosecond X-ray spectroscopy of haem proteins

Ultrafast Energy Transfer from Photoexcited Tryptophan to the Haem in Cytochrome c

Threshold and cage effect for dissociation of H2O and D2O in Ar and Kr matrices

Investigation of nanolocal fluorescence resonance energy transfer for scanning probe microscopy

Observation of coherent cage motion in electronically excited doped argon and hydrogen crystals

Three pulse UV photon echo studies of molecules in solution: Effect of the chirp

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

High density excitation of rare gas crystals for stimulated emission

Mapping the thermo-induced valence tautomerism in Cobalt dioxolane single crystals

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

Ultrafast dynamics of Rydberg states in the condensed phase