SOURCES OF PARTICLES

Author: FERNÁNDEZ CAÑOTO DAVID.
Year: 2005.
University: VIGO [www.uvigo.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In this thesis is presented a study of the dynamics for the single particle of water confined in the xerogel determined by using the same technique dispersion Neutrones Highly Inelástica (DINS). In particular, we will examine the distribution of the times of protons confined water in the pores interstitial where (are typical diameter by about 24 Angstroms and 82 Angstroms) of a dust xerogel. The xerogel is a derivative of silica and transparent, which can be produced in a wide range of densities macroscopic with controlled porosity. You can change the average size of the micro-pores in the middle of the structure, and thus provide a model system to investigate the dynamic properties of hidrógenos trapped. The water was confined in a crystal of silica sol-gel (xerogel) with two different pore size in order to study the dynamics of protons for two different sizes of confinement and determine possible changes induced in the environment of protons in the water. The objective of this study was developed to understand how the connected networks of links hydrogen modified when water is confined in small cavities within a material substrate as the xerogel. The experiments were performed with the water contained in matrices xerogel with two different pore size, called xerogel 24 Ay xerogel 82 A with average pore diameter of 24 A and 82 A, respectively, using the VESUVIO, a reverse geometry spectrometer operating the source of neutrons for breath at ISIS (Rutherford Appleton Laboratoy, United Kingdom). The measures were developed in the samples hydrated and dried, whose hydration levels were 108% and 26% for the xerogel 24 Ay xerogel 82 A, respectively. The experiments were performed in the range of when transferred, q, and energy transferred, w, 20 A-1 minor q smaller 250 A-1 and 1 eV lower w minor 20eV $, respectively (h = 1). Final results for the experiments conducted in the dry and hydrated samples of xerogel 24 Ay xerogel 82 A, have shown an increase of the kinetic energy disminuimos half when the pore size. Contributions from the dried samples had to be substraídas and a more precise value for water confided was calculated. The specter of hydrogen in the samples hydrated is due to two distinct contributions, those from the water introducid ay those belonging to groups silanol of xerogel dry. Water confined in the xerogel 24A has an average kinetic energy of the proton lower greater Ek = 170.9 + - +-16.2 meV, being higher than that for the bulk water and also that the xerogel 82 A, which has presented Ek = 156.4 +-8.5 meV. Therefore confinement of the protons of hydrogen leads to a dramatic increase in kinetic energy mean, where virtually the NCP have a major contribution from the component vibrational, and those vibrations type stecht from hydrogen bond. Comparing results was also important to establish a relationship between the levels of hydration of the samples, we found that it is not significant when this parameter to study the effects of confinement, the degree of hydration in experiments conducted by the spectrometer VESUVIO.