Helen Silva

Espectroscopia de fotoelétrons de limiares de átomos e moléculas

A threshold photoelectron spectrometer applied to the study of atomic and molecular threshold photoionization processes is described. The spectrometer has been used in conjunction with a toroidal grating monochromator at the National Synchrotron Radiation Laboratory (LNLS), Brazil. It can be tuned to accept threshold electrons (< 20 meV) and work with a power resolution of 716 (~18 meV at 12 eV) with a high signal/noise ratio. The performance of this apparatus and some characteristics of the TGM (Toroidal Grating Monochromator) beam line of LNLS are described and discussed by means of argon, O2 and N2 threshold photoelectron spectra.

Low Energy Electron Scattering from Polyatomic Targets

Low energy elastic electron scattering cross-sections from water and several alcohols are presented. This paper addresses accurately measuring quantitative differential elastic scattering cross-sections, using the relative flow method with an aperture source, and focuses on the long range dipole interaction of the scattering electron with these polar targets. The electron-dipole interaction dominates the scattering for these molecules and contributes significantly to their integral elastic cross-sections.