Mise en évidence d'états excités dans les spectres de photoionisation du cyclohexane et du diméthyl 2-2-butane liquides

Excited states are probably occurring, at an intermediate stage, in the VUV photoionization process of liquid hydrocarbons, as suggested by a Stern-Volmer behaviour when interacting with electron quenchers. They are here detected in the VUV photoionization spectrum of cyclohexane and dimethyl-2-2-butane in liquid phase. Some of the discernable peaks can be assigned as valence and Rydberg states, yet observed in gas phase. Supplementary peaks are observed, the existence of which is to be interpretated.L'existence d'états excités dans le processus de photoionisation VUV des hydrocarbures en phase liquide - précédemment suggérée par l'observation de la loi de Stern-Volmer lors de l'interaction avec des capteurs d'électrons - est ici détectée en traçant le spectre de photoionisation VUV du cyclohexane et du diméthyl-2-2-butane purs en phase liquide. Certains des pics observés coïncident avec les états de valence et de Rydberg de ces mêmes corps en phase gaz. Il apparaît des pics supplémentaires dont la nature doit être précisée

V.U.V. Photoionization process in non polar dielectric liquids

The present paper must be considered as an overwiew on our recent or more ancient works about photoionization processes in non-polar liquids. The main points examined are : - Determination of the conduction level in the liquid phase : Vo. - Determination of the ionization threshold and the power laws of the photocurrent as a function of the excess energy of photons. - Determination of photoionization parameters i.e. : photoionization quantum yield and thermalization distance of photoelectrons. - Estimation of the spatial distribution function of photoelectrons, around their geminate positive ion. - The possible existence of metastable spatially extended excited states (Rydberg states) above the liquid ionization threshold. Here we examine which of our works are simple pieces of well supported theories, which are a contribution to more opened questions

The effect of metal-cation vacancies on vanadium antimonate surface properties. A theoretical study

In this work, we studied the distribution of V and Sb vacancies in the rutile-type vanadium antimonate phase and the influence of these cationic defects on the VSbO4(110) surface properties. We performed density functional theory (DFT) calculations to compute the energy stability of bulk supercells with different geometrical arrangements of the metal-cation-deficient sites. Then, we built a model of the nonstoichiometric VSbO4(110) surface, which exhibited an extra O layer and isolated V cations—V atoms surrounded by Sb ions—that could act as Lewis acid sites. The density of states (DOS) plot of this surface showed contributions of O(2p) states, coming from surface O atoms nearest-neighbor of a V vacancy, and V(3d) states near the Fermi level. We also studied the influence of cation-vacancies in the formation of Brønsted acid sites.Fil: Seitz, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina; Universidad Nacional del Sur. Departamento de Física; Argentina;Fil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina; Universidad Nacional del Sur. Departamento de Física; Argentina;Fil: Brizuela, Graciela Petra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina; Universidad Nacional del Sur. Departamento de Física; Argentina;Fil: Irigoyen, Beatriz del Luján. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; Argentina