Laboratoire Francis PERRIN
URA CNRS-CEA 2453
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The GOUTTELIUM setup : an IR spectroscopy in a cold environment
Last Update: 29 July 2014

Etude du photorécepteur "Photoactive Yellow Protein" par dichroïsme circulaire femtoseconde
Last Update: 21 February 2016

L'interaction médicament-protéine étudié par spectroscopie de fluorescence résolue en temps
Last Update: 9 December 2013

"Cœur silicium - coquille carbone" pour batteries Li-Ion
Last Update: 6 October 2015

Dynamic of peptids in gas phase and photostability of proteins
Last Update: 21 May 2013

A method to observe the complete vibrational spectrum of ionized molecules
Last Update: 21 May 2013

The strength of the NHamide---Smethionine revealed by spectroscopy of small peptides
Last Update: 21 May 2013

Imagerie photochimique du champ proche optique de nanocubes d’or
Last Update: 15 March 2012

Des tapis de nanotubes alignés, en grande surface !
Last Update: 31 January 2012

Nouvelles lumières sur l’interaction entre les rayons UVA et l’ADN
Last Update: 3 February 2014

Synergy btetween experiment and theory for the simulation of protein folding
Last Update: 21 September 2010

Un nouveau composé aux propriétés intéressantes d'absorption optique dans le domaine visible : TiO
Last Update: 17 June 2010

Synthèse de nanotubes marqués au carbone 14 pour des études de biodistribution
Last Update: 13 January 2011

A surprising dynamic of cluster fragmentation
Contact : Lionel Poisson (LFP) et

Clusters consists in a set of several up to million atoms in condensed phase with nanometric finite size. The investigation of their properties as the function of their increasing size is sometimes presented as one way to build a macroscopic condensed world from a gas. This often appears to be too simplistic, because the static and dynamic behavior of clusters has often no equivalence at the macroscopic scale, as they are controlled by their high specific surface and their finite size. These concerns the physical chemistry of the mesoscopic world, as illustrated by the recent experimental study driven by the "Reaction dynamics" group of DRECAM/SPAM-Laboratoire Francis Perrin in collaboration with a theoretician team from Paris VI University.

 

A femtosecond laser pulse, of intermediate intensity (≈ 1013 W cm-2), focused on a cluster consisting of several hundred argon atoms (ArN where N is the number of atoms of the cluster) can lead to its explosion. In one original reaction path, which has just been identified, the coulombian explosion of the cluster results from the initial formation of two very close positive ions inducing the formation of two asymmetric ionic clusters: a small one with 1 to 4 atoms and a larger one including several dozen of atoms. The speed distribution of the fragments shows that the explosion mechanism of the two charges requires an initial excitation during the laser interaction within an highly excited ionic state which relaxation induces the ionization of one neighbor atom. Both charges so formed repelled together forming, with surrounding atoms, the two emitted ionic clusters. This result is a priori very surprising because the observed phenomenon imposes a high localization of the initial energy. The observed dissociation does not correspond to that of a solid or a liquid where a statistical distribution of excess energy leading to a gradual evaporation of the cluster would be observed, but a brutal fission.

 
Chemin réactif de la fission d\

Chemin réactif de la fission d'un agrégat

Figure : Speed distribution of Ar15+ ions emitted from an aggregate of approximately 750 atoms after irradiation by a femtosecond laser. R is proportional to the velocity of the ions emitted in the direction θ with respect to the direction of the polarization of the laser light. The color intensity scale is linear and proportional to the number of ions. The rings of this figure shows that the Ar15+ ions are isotropically emitted. The three rings indicate three clearly distinct classes of speed, according to the mass and energy of the recoil fragment formed (Ar+ to Ar3+). The central spot corresponds to the simple ionization of the cluster.

Reference :
Low field laser ionization of argon clusters: the remarkable fragmentation dynamics of doubly ionized clusters,
L. Poisson, K. D. Raffael, M.-A. Gaveau, B. Soep, J.-M. Mestdagh, J. Caillat, R. Taïeb, and A. Maquet, Phys. Rev. Lett. 99, 103401 (2007).

 

Chirality and folding of peptide chains
Last Update: 23 March 2007

Recent results in physicochemistry with the very new laser PLFA
Last Update: 16 March 2007

Effets coopératifs dans l'absorption du rayonnement UV par les bases de l'ADN
Last Update: 3 February 2014

Repliement de chaînes peptides en détente supersonique
Last Update: 3 February 2014

Formation of carbon nanotube multi-layers and identification of their growth mode
Last Update: 5 January 2010

Participation d'un état de Rydberg à la redistribution ultrarapide de l'énergie électronique du TDMAE [tetrakis(diméthylamino)éthylene]
Last Update: 3 February 2014