Publications de Amal El Nahhas

X-ray Absorption Spectroscopy of Ground and Excited Rhenium–Carbonyl–Diimine Complexes: Evidence for a Two-Center Electron Transfer

Majed Chergui, Ursula Röthlisberger, Ivano Tavernelli, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima, Thomas James Penfold

Steady-state and picosecond time-resolved X-ray absorption spectroscopy is used to study the ground and lowest triplet states of ReX(CO)(3)(bpy), X = Etpy (n = 1), Cl, or Br (n = 0). We demonstrate that the transient spectra at both the Re L3- and Br ...

Amer Chemical Soc2013

Re and Br X-ray Absorption Near-Edge Structure Study of the Ground and Excited States of [ReBr(CO)(3)(bpy)] Interpreted by DFT and TD-DFT Calculations

Amal El Nahhas, Renske Marjan van der Veen

X-ray absorption spectra of fac-[ReBr(CO)(3)(bpy)] near the Re L-3- and Br K-edges were measured in a steady-state mode as well as time-resolved at 630 ps after 355 nm laser pulse excitation. Relativistic spin-orbit time-dependent density functional theory ...

American Chemical Society2013

A wavelet analysis for the X-ray absorption spectra of molecules

Majed Chergui, Ursula Röthlisberger, Ivano Tavernelli, Amal El Nahhas, Marco Eli Reinhard, Thomas James Penfold

We present a Wavelet transform analysis for the X-ray absorption spectra of molecules. In contrast to the traditionally used Fourier transform approach, this analysis yields a 2D correlation plot in both R- and k-space. As a consequence, it is possible to ...

American Institute of Physics2013

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

Majed Chergui, Olivier Christian Bräm, Amal El Nahhas, Andrea Cannizzo, Cristina Consani

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 ...

2011

Origin of electronic absorption spectra of MLCT-excited and one-electron reduced 2,2 '-bipyridine and 1,10-phenanthroline complexes

Majed Chergui, Amal El Nahhas, Andrea Cannizzo, Cristina Consani

UV-Vis absorption spectra of one-electron reduction products and (MLCT)-M-3 excited states of [(ReCl)-Cl-I(CO)(3)-(N, N)] (N, N = 2,2'-bipyridine, bpy; 1,10-phenanthroline, phen) have been measured by low-temperature spectroelectrochemistry and UV-Vis tran ...

Elsevier2011

Ultrafast (Bio)physical and (Bio)chemical Dynamics

Majed Chergui, Olivier Christian Bräm, Frank van Mourik, Amal El Nahhas, Andrea Cannizzo, Ahmad Ajdar Zadeh Oskouei, Renske Marjan van der Veen, Cristina Consani, Gerald Auböck

We give an overview of our recent work on ultrafast dynamics of chemical (organic dyes, metal-complexes, colloidal quantum dots), and biological (retinal and haem proteins) systems in the liquid phase, studied with a variety of ultrafast optical techniques ...

2011

Probing the Transition from Hydrophilic to Hydrophobic Solvation with Atomic Scale Resolution

Majed Chergui, Paul Beaud, Ivano Tavernelli, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima, Thomas James Penfold

Picosecond and femtosecond X-ray absorption spectroscopy is used to probe the changes of the solvent shell structure upon electron abstraction of aqueous iodide using an ultrashort laser pulse. The transient L-1,L-3 edge EXAFS at 50 ps time delay points to ...

2011

Time-Resolved Optical and X-Ray Spectroscopy of Rhenium Based Molecular Complexes

Amal El Nahhas

The photocycle of rhenium carbonyl complexes, type facial-[Re(L)(CO)3(diimine)]n [L=halide / n=0, L=4-Ethyl-pyridine (Etpy)- Imidazole (ImH) /n=+1, diimine= bpy , 10- phenanthroline (phen), 4,4'-dimethyl-2,2'-bpy (dmb)] was studied using a set of ultrafast ...

EPFL2010

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

Majed Chergui, Paul Beaud, Wojciech Gawelda, Camelia Borca, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

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 ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2009

Vibrational coherences and relaxation in the high-spin state of aqueous [Fell(bpy)3]2+

Majed Chergui, Frank van Mourik, Amal El Nahhas, Andrea Cannizzo, Mirabelle Prémont-Schwarz, Cristina Consani

Dizzy cooling: Femtosecond excitation of the singlet states of aqueous [FeII(bpy)3]2+ (bpy=2,2-bipyridine) leads to the formation of a vibrationally hot quintet state that exhibits wave-packet dynamics arising from a chelate-ring and bending mode. The vibr ...

Wiley-VCH Verlag GmbH2009

Structural determination of photochemically active diplatinum molecule by time-resolved EXAFS spectroscopy

Majed Chergui, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

Metallica: A large contraction of the PtPt bond in the triplet excited state of the photoreactive [Pt2(P2O5H2)4]4- ion is determined by time-resolved X-ray absorption spectroscopy (see picture). The strengthening of the PtPt interaction is accompanied by a ...

Wiley-VCH Verlag GmbH2009

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

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

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 ...

American Association for the Advancement of Science2009

Retrieving photochemically active structures by time-resolved EXAFS spectroscopy

Majed Chergui, Wojciech Gawelda, Camelia Borca, Amal El Nahhas, Van Thai Pham, Renske Marjan van der Veen, Frederico Alves Lima

Describing the nature and structure of molecular excited states is important in order to understand their chemical reactivity and role as intermediates in photochemical reactions. The recent implementation of x-ray absorption spectroscopy in the ultrafast ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2009

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

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

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

Capturing transient electronic and molecular structures in liquids by picosecond X-ray absorption spectroscopy

Majed Chergui, Wojciech Gawelda, Amal El Nahhas, Van Thai Pham

We describe an advanced setup for time-resolved x-ray absorption fine structure (XAFS) spectroscopy with picosecond temporal resoln. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of th ...

2007