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In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell&ndash, Wagner polarization effects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S11 reflection measurements. An experimental sensitivity of 820 &nbsp, MHz . g &minus, 1 . cm 3 was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S11 level at low frequency or the electrical conductivity to extract the density from the frequency measurements.

The resonant double photoionization of Ne has been studied via an electron-electron coincidence experiment. A complete set of measurements was performed at different mutual angles when the photoelectron and Auger-electron pairs have nearly equal energy. The overall experimental energy resolution, narrower than the natural linewidth of the intermediate state, has allowed us to observe interference effects due to the indistinguishability of the two electrons. The observed energy and angular distribution exhibit a strong interplay of postcollisional interaction and interference effects. Calculations based on the model developed by Sheinerman and Schmidt [J. Phys. B 30, 1677 (1997)] describe the main trend of the experimental observations.

The combined effects of post-collision interaction in the final state and interference due to the indistinguishability of the two electrons have been studied in a selected case of resonant double photoionization of neon. In our coincidence experiments, the photo- and Auger-electron pair was measured when the two electrons have nearly equal energy and are ejected at small mutual angle. The obtained energy distributions exhibit a strong interplay of post-collision interaction and interference effects, in agreement with the theoretical prediction of Sheinerman and Schmidt [J. Phys. B 30, 1677 (1997)] made on beryllium.

The resonant double photoionization of Ne has been studied via an electron-electron coincidence experiment at a photon energy of 92.71 eV. At this energy, the kinetic energy of the photoelectrons matches exactly the energy of the Auger electrons. The overall experimental energy resolution, narrower than the natural linewidth of the intermediate state, has allowed us to observe angular- and energy-dependent interference effects due to the indistinguishability of the two electrons.

This work presents the implementation of a position-sensitive detector in the Montelibretti surface (e,2e) apparatus that allows to fully define the direction of the ejected electron from the surface, and hence to improve the momentum resolution. The coincidence electronic chain and the acquisition software have been upgraded in order to achieve high data collection speed, storage of large dimension data files and fast visualisation of the results. Preliminary angle resolved (e,2e) data relative to the ionisation of the pi band of highly oriented pyrolitic graphite show that a momentum resolution better than 0.2 Angstrom(-1) has been achieved without degrading the overall speed of acquisition.

The capability of grazing angle (e,2e) experiments to map momentum distribution is demonstrated.: This is an application of reflection (e,2e) experiments as a unique twofold spectroscopy, binding energy and momentum distribution, for solid surfaces. The reported experiments have been performed on highly oriented pyrolytic graphite at about 300-eV incident energy, grazing angle, and for ejected electron energies ranging from 3.7 to 30 eV. These experiments, interpreted in the framework of the plane-wave impulse approximation, yield the binding energy vs momentum dispersion curves of valence electron states as well as the individual pi-state momentum density. Both results compare favorably with calculated graphite band structure. [S0163-1829(98)06404-2].