Grand Séminaire d'Institut

Vendredi 24 Mai 2019 à 11h00.

Inferences from trapped ion experiments: Intrinsic photo physical properties of chromophores and structural variations of metal clusters.

''Experiments in ion traps enable studies of physical and chemical properties of molecular- and cluster-ions in a well-defined environment thus shedding light on the intrinsic properties of the system under study and allow for direct comparison with theoretical predictions.
In the first part of this talk I will review our work on laser induced fluorescence of trapped ions (TLIF) focusing on the intrinsic triplet lifetimes of Rhodamine cations, which are found to be on the order of seconds, several orders of magnitude longer than typically found for the same dyes in optical condensed phase measurements. In addition dispersed luminescence measurements and luminescence decay analysis of lanthanide complexes are provided and the impact of the complex stoichiometry on its optical properties is discussed.
In the second part I will present the structural evolution of bare and hydrogenated Ru-clusters determined by trapped ion electron diffraction (TIED). While for the bare clusters hexagonal layered or close packed fcc structures were found, hydrogenation changes the structure type of the ruthenium core towards an icosahedral motif. Density functional theory computations reveal the driving force behind this process to be the larger hydrogen adsorption energies for the icosahedral structure type. TIED measurements indicate that the hydrogen induced structure change extends up to ~ 200 ruthenium atoms - a size range which is identical to the onset of catalytic activity for Ru-based ammonia synthesis.''