Soutenance de thèse Olivier Durif

Un nouvel instrument pour étudier la cinétique et les rapports de branchement des collisions réactives entre espèces neutres dans les écoulements supersoniques uniformes

Résumé :

Despite major advances in our understanding of physico-chemical processes leading to the formation of the great diversity of molecules observed in astrophysical environments, many mechanisms remain to be elucidated. One of the current challenges is to quantitatively determine the products of gas phase reactions at low temperatures. To this end we have developed a new instrument for the study of both the production of molecular clusters and radical-neutral reactions in temperatures range 10-100K. The objective is twofold: (i) measure temperature-dependent kinetics rate coefficients (ii) determine the branching ratios of the reaction products between molecules and radicals.  This instrument combines a uniform supersonic flow reactor (CRESU) and a time-of-flight mass spectrometer with a photoion-photoelectron coincidence scheme (PEPICO). All the setup is transportable to be plugged to a synchrotron radiation in the vacuum ultraviolet (DESIRS beamline at SOLEIL). The present work conducted at SOLEIL on the DESIRS beamline has demonstrated the capabilites of the CRESUSOL instrument. For the first time is reported the bimolecular rate coefficient of formation of the formic acid dimer (HCOOH)2 at a temperature of 50 K.

Composition du jury :

Rapporteurs : Fabien Goulay, Patrick Rousseau
Examinateurs :  Christa Fittschen, Astrid Bergeat
Directeurs de thèse : Sébastien Le Picard, Ludovic Biennier