Publications de Erwin Portuondo Campa

Functional electric field changes in photoactivated proteins revealed by ultrafast Stark spectroscopy of the Trp residues

Stefan Haacke, Majed Chergui, Frank van Mourik, Erwin Portuondo Campa, Andrea Cannizzo

Ultrafast transient absorption spectroscopy of wild-type bacteriorhodopsin (WT bR) and 2 tryptophan mutants (W86F and W182F) is performed with visible light excitation (pump) and UV probe. The aim is to investigate the photoinduced change in the charge dis ...

2009

Ultrafast nonresonant response of TiO2 nanostructured films

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

The authors present a detailed study of the nonresonant 3rd-order ultrafast response of TiO2 nanostructured films, combining a classical heterodyned optical Kerr effect expt., with 2 polarization selective Kerr techniques, based on transient lensing and ph ...

2008

Optical Kerr effect studies of the dynamics of confined water

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Time resolved optical Kerr effect measurements have been used to det. the orientational dynamics of water in the pores of ZrO2 nanostructured films. We demonstrate that local heating effects can safely be ignored and present our results which are manifestl ...

2008

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

Majed Chergui, Frank van Mourik, Wojciech Gawelda, Erwin Portuondo Campa, Andrea Cannizzo, Andrea Callegari

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 ...

2008

Liquid dynamics in ZrO2 nanoporous films

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

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 ...

2007

On the excitation wavelength dependence of the fluorescence of bacteriorhodopsin

Stefan Haacke, Majed Chergui, Selma Schenkl, Erwin Portuondo Campa, Goran Zgrablic

We present a systematic study of the time-integrated fluorescence of native bacteriorhodopsin, as a function of excitation wavelength across the visible absorption band. While the fluorescence max. is unaffected, the spectrum broadens on the high-energy si ...

Elsevier2007

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

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

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 ...

Elsevier2006

Aqueous Solvation Dynamics at Metal Oxide Surfaces

Jacques-Edouard Moser, Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

Broadband transient absorption (TA) spectroscopy, three-pulse photon echo peak shift (3PEPS), and anisotropy decay measurements were used to study the solvation dynamics in bulk water and interfacial water at ZrO2 surfaces, using Eosin Y as a probe. The 3P ...

2006

Solvation dynamics at liquid/metal-IV oxide interfaces

Erwin Portuondo Campa

This thesis presents a comparative study of the ultrafast solvation dynamics of liquids in bulk conditions, and at the interfaces of metal-IV oxides (specifically TiO2 and ZrO2), using ultrafast spectroscopy techniques. In the first part of the thesis we r ...

EPFL2006

Absorption spectroscopy of three-dimensional bacteriorhodopsin crystals at cryogenic temperatures: effects of altered hydration

Majed Chergui, Selma Schenkl, Erwin Portuondo Campa

A comparative study of absorption spectroscopy at 100 K has been performed on three-dimensional crystals of bacteriorhodopsin extd. from a lipidic cubic phase and on native purple membrane. A modified microspectrophotometer has been designed which yields a ...

2006

Raman-induced signals in optical Kerr effect measurements of water with elliptically polarized pulses

Majed Chergui, Frank van Mourik, Erwin Portuondo Campa

In 2-color optical Kerr effect measurements of water, addnl. signals can occur in the pulse overlap region if the energy difference between pump and probe pulses approaches the Raman resonance of the OH-stretch vibration. These features can be understood b ...

2006