Simulation of dissociation and caging inside helium clusters
Résumé
The dissociation dynamics of molecules embedded in a condensed matter matrix is theoretically and experimentally well studied for macroscopic situations. Generally, excitation above a
molecular fragmentation limit can lead to two scenarios depending on the details of the energy dissipation dynamics. The first one is fast recombination (the cage effect, see for example [1])
and the second the long time survival of separated fragments. In a cluster environment a third scenario becomes possible, namely fragments leaving the cluster with or without attached cluster
particles. Helium clusters are a very cold (about 0.5 K) but still liquid and dense environment with particularly challenging properties due to the pronounced collective quantum behavior of
helium leading to unusual energy dissipation dynamics. We present first results of simulations of the photodissociation of molecular iodine, I2, at various excitation energies inside helium
clusters with several thousand atoms using a technique based on quantum effective potentials [2] to account for the quantum effects. We obtain cluster size dependent threshold energies for
caging, velocity distributions of photofragments exiting from the clusters and statistics about the number of helium solvent atoms carried along by the iodine atoms similar to experimental
results obtained for CH3I [3].
Domaines
Chimie théorique et/ou physique
Origine : Fichiers produits par l'(les) auteur(s)