Seção de choque total do espalhamento de elétrons por metano e etano

Abstract

Were obtained in this work values of total cross-section (TCS) of electron impact on methane and ethane using a device developed at the Atomic and Molecular Spectroscopy Laboratory (LEAM) - DF - UFJF employing the linear transmission technique. These data reflect the total scattering probability of incident electrons that penetrate a gaseous medium with a wide range of applications, such as the development of lasers, plasma physics, gaseous electronics, astrophysics, studies of Earth's outer atmosphere and semiconductors. A low-energy electron gun continuously covering the energy from 20 to 250 eV was built to obtain these measures with an energy resolution of 0.6 eV and current intensity of the order of units to hundreds of ƞA. The measurements were performed for methane and ethane covering the energies of 100, 110, 120, 130 and 150 eV and 90 eV also for ethane. Starting from mean attenuation of the electron beam that pass through a cell filled with gas to be studied, the SCT was obtained by applying the Beer-Lambert Law. The electrons that have not been scattered were discriminated from those scattered by a 127º cylindrical dispersive analyzer before being detected by a Faraday Cup. The necessary data to perform the calculation of TCS to a specific energy value was obtained through a statistical process involving a range from 5 to 10 acquisition turns. In addition to the experimental measurements, the SCT was determined by the semi-empirical formula of García and Manero. It was also proposed a new acquisition technique of SCT by detecting the scattered electron beam that reaches the walls of the scattering cell. The data were compared with those available in literature and the calculated ones. TCS values obtained in this study showed relative agreement with the literature.