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Collisions agrégats-molécules : attachement, fragmentation, nanocalorimétrie

Isabelle Braud 1
1 Agrégats (LCAR)
LCAR - Laboratoire Collisions Agrégats Réactivité
Abstract : The experimental set-up developed in Toulouse enables to control collisions between a charged thermalised mass-selected free cluster and molecules. Processes of attachement of the molecule onto the cluster and collision induced fragmentation can be studied. In order to better understand the process of attachment of a molecule onto a cluster, we have measured attachment cross-sections of alcohol molecules, methanol and ethanol, onto alcohol clusters.We have observed a similar behaviour as the one observed with water clusters, that is attachment cross-sections that are lower than the geometrical cross-section at small sizes and that converge to this geometrical cross-section at bigger sizes. This behaviour had been assigned to a dynamical effect in the case of water. This dynamical model can be extended with a good qualitative agreement to alcohol clusters. Processes of attachment and fragmentation enable to realise nanocalorimetry measurements. We have determined heat capacities and transition temperatures for protonated water clusters (H2O)nH+. They complete measurements already done for deprotonated water clusters (H2O)n-1OH-. The nature of the phase transition is discussed. The last part of this dissertation concerns collision induced fragmentation for molecules that have some biological interest : protonated uracil, bare or hydrated. Fragmentation pathways of the protonated uracil molecule has been observed. The influence of the number of water molecules on the fragmentation pattern of solvated uracil is linked to the proton affinity of the constituants and to the cluster structure.
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https://tel.archives-ouvertes.fr/tel-01388605
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Submitted on : Thursday, October 27, 2016 - 11:50:22 AM
Last modification on : Wednesday, November 3, 2021 - 4:11:57 AM

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  • HAL Id : tel-01388605, version 1

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Isabelle Braud. Collisions agrégats-molécules : attachement, fragmentation, nanocalorimétrie. Physique [physics]. Université Toulouse 3 Paul Sabatier, 2016. Français. ⟨tel-01388605⟩

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