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Principles of Electron Energy Loss Spectroscopy and its Application to the Analysis of Paper
Published in Terrance E. Conners, Sujit Banerjee, Surface Analysis of Paper, 2020
In elastic scattering, the incident electron trajectory is modified by the electrostatic potential of the nucleus by Coulomb interactions (also known as Rutherford scattering) and its energy is unchanged. Other processes for which the energy lost by the electron cannot be practically measured using current technology are also, in general, classified as elastic. For example, interactions with lattice vibrations (phonons) in which the energy lost is in the order of few meV are considered “quasi-elastic” and fall into this class of scattering. Mathematically, the elastic scattering can be described by a cross-section a(0) calculated from first principles that predict the probability of an electron being scattered at an angle θ (Figure 1). Related to this quantity, a mean free path λo can be used to represent the (mean) distance travelled in the solid between consecutive scattering events of the incident electron. With 100 keV incident electrons and for a low atomic number element such as carbon, λo is in the order of 200 nm, but for higher Z elements it is significantly lower (for Cu λo ≈ 20 nm).4 It is important to note that in solids, the angular distribution of scattered electrons cannot be solely described by σ(θ), which is derived for single isolated atoms as the periodicity of the lattice gives rise to electron diffraction. The angular distribution is therefore modified to include Bragg reflections. However, in amorphous solids the atomic σ(θ) can be considered to be approximately representative of the scattering distribution.
Quantum Primer
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Collisions of atoms constantly occur in gases, liquids, and solids. Particle collisions are the bread and butter of particle physics. For particles too small to see with a microscope, particle-particle collsion experiments and theoretical analysis offers scientists one of few ways to determine particle properties. The discovery of the “Rutherford atom” was made by collision experiments, Rutherford scattering, and first showed that an atom had a small, heavy nucleus surrounded by light electrons. Electrons were found to be light through collisions with heavier particles. Today, particle physicists are looking for the Higgs boson, the particle thought to be responsible for the fact that matter has mass, as a constitutive part of more common subnuclear particles. The understanding we have of the microscopic world stems largely from collision experiments done in the twentieth century. The quantitative description of these collisions has been largely based on quantum mechanics.
Rutherford and the Cavendish Laboratory
Published in Journal of the Royal Society of New Zealand, 2021
Rutherford's great years from 1898 to 1919 saw a number of key experiments and results which established his reputation as an experimenter of genius. They included: The elucidation of radioactive decay chains with the chemist Frederick Soddy. For this work, he was awarded the Nobel Prize in Chemistry in 1908.An estimate of the age of the Earth from long-lived radioactive species.The demonstration that α-particles are the same as the nuclei of helium atoms.The discovery of the nucleus of the atom from the scattering of α-particles through the process now known as Rutherford scattering.The measurement of e/m for α-particles.the first demonstration of the artificial destruction of nitrogen nuclei by energetic α-particles.These pioneering experiments are a tribute to Rutherford's outstanding ability to carry out simple experiments which, carried out with very great care and persistence, opened up new areas of experimental and theoretical research.