A novel experimental method for the measurement of the caloric curves of clusters

A novel experimental scheme has been developed in order to measure the heat capacity of mass selected clusters. It is based on controlled sticking of atoms on clusters. This allows one to construct the caloric curve, thus determining the melting temperature and the latent heat of fusion in the case of first-order phase transitions. This method is model-free. It is transferable to many systems since the energy is brought to clusters through sticking collisions. As an example, it has been applied to Na\_90\^+ and Na\_140\^+. Our results are in good agreement with previous measurements

La collision reactive Cs*+H_2#->#CsH+H: etude experimentale en jets croises et calculs de trajectoires classiques

SIGLEINIST T 74805 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Macroscopic extension of RRK and Weisskopf models of unimolecular evaporation

The macroscopic behavior of two microscopic unimolecular evaporation models is examined. The temperature dependences of bulk equilibrium vapor pressures deduced from the Rice-Ramsperger-Kassel (RRK) model and from the Weisskopf model, respectively, are compared. The bulk vapor pressures of sodium given by both models are compared, over a wide temperature range, with the experimental vapor pressures. The Weisskopf model is in better agreement with the experimental data than the RRK theory: from the melting temperature to the critical temperature (∼ 370 K–2500 K), the vapor pressures of sodium calculated using the Weisskopf model agree with experimental values within 2%, whereas the RRK theory leads to errors of more than 40%. The Weisskopf theory satisfying the detailed balance principle, whereas the RRK theory does not, may explain this result

EFFETS DES OESTROGèNES SUR LA SéCRéTION DE PROLACTINE

info:eu-repo/semantics/publishe

A two-state model analysis of the melting of sodium clusters: Insights in the enthalpy-entropy compensation

International audienceExperimental melting temperatures and associated latent heats of size-selected sodium clusters are analyzed in the frame of a two-state model of melting. The strong variations of these quantities as a function of size make clusters an excellent benchmark for testing speculative ideas about melting. The relation between cohesive energy of clusters and their latent heat of melting is demonstrated, and a correlation between cohesive energy and vibrational frequency in the solid state is found. It is shown that this relation may throw light on the enthalpy-entropy compensation, which is observed in a variety of systems undergoing a first-order phase transition. A relation is established between the Lindemann melting criterion, the variation of the vibrational frequency with the cohesive energy, and the enthalpy-entropy compensation

Processus élémentaires de nucléation (un outil pour l'étude des transitions de phases dans les agrégats)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Reaction to thyrotropin-releasing hormone (TRH) in anterior pituitay failure

info:eu-repo/semantics/publishe