Université Paul Sabatier - Bat. 3R1b4 - 118 route de Narbonne 31062 Toulouse Cedex 09, France

Accueil > Séminaires > 2014

Spectroscopy to probe cluster structure and dynamics : Theoretical investigations

Gilles Peslherbe, Concordia University (Montréal, Canada)

Séminaire LCPQ

Salle de séminaire IRSAMC

Charged aqueous clusters provide an especially useful paradigm for the detailed investigation of the ion–water and water–water interactions involved in numerous important biological and chemical processes. In this contribution, the use of state-of-the- art computer simulations in conjunction with vibrational and time-resolved photoelectron spectroscopy is explored as a powerful approach to probe cluster structure and dynamics.

Vibrational spectroscopy along with complementary computer simulations has long been used to understand the structural properties of clusters. Accurate first- principles molecular dynamics simulations and computations of the vibrational spectra of ion-water clusters are first discussed, and connection with available experimental data is made to unambiguously assign structural motifs of the ion-water clusters. The structural motifs of different ion-water clusters are compared to unveil the factors that could possibly govern the hydration structure of different ions.

Time-resolved photoelectron spectroscopy on the other hand has been employed in recent years to probe the dynamics of aqueous clusters. Photoexcited iodide-water clusters have attracted considerable interest, since investigation of these clusters may provide new insights into the mechanism of formation of the closely related hydrated electron, one of the simplest yet most mysterious ions of chemistry. Ab initio molecular dynamics simulations of the excited-state dynamics of iodide-water clusters are presented ; the use of these simulation results along with experimental photoelectron spectra to understand the precise mechanism of excitation and relaxation is then discussed. The cluster structure and dynamics may be understood in terms of the subtle interplay between the water-water and ion-water interactions in the cluster.