Lecture

Chemical Analysis: X-Ray Micro-Analysis XRMA

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In course

CH-410: Physical and chemical analyses of materials

The course relates on the use of electromagnetic (X-Ray) and corpuscular (electrons) radiations for physical and chemical analysis of solid materials. ...

Description

This lecture covers X-Ray Micro-Analysis (XRMA), a technique analyzing X-rays emitted by matter when excited by an electron beam. It compares XRMA in electron microscopes (EM) with specific spectrometers like EMPA, discussing sensibility, accuracy, and interaction between electrons and matter. The lecture explains the interaction volume, primary emission, X-Ray fluorescence, and matter excitation-relaxation. It details the analysis of thick and thin materials, matrix effects, and correction methods for quantitative analysis. The XRMA spectrometers, operating modes, and sources of errors are also discussed, along with qualitative and quantitative analysis methods for thick and thin samples.

Instructor

Christophe Roussel

Habilitation à Diriger les Recherches (HDR) in chemistry at the Ecole Normale Supérieure Paris-Saclay (Cachan, France)PhD Thesis in physical organic chemistry at the University of Bourgogne Franche-Comté (Besançon, France) / Ecole Normale Supérieure Paris-Saclay (Cachan, France)

Official source

Related concepts (32)

Electron microscope

An electron microscope is a microscope that uses a beam of electrons as a source of illumination. They use electron optics that are analogous to the glass lenses of an optical light microscope. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light, electron microscopes have a higher resolution of about 0.1 nm, which compares to about 200 nm for light microscopes.

Low-voltage electron microscope

Low-voltage electron microscope (LVEM) is an electron microscope which operates at accelerating voltages of a few kiloelectronvolts or less. Traditional electron microscopes use accelerating voltages in the range of 10-1000 keV. Low voltage imaging in transmitted electrons is possible in many new scanning electron detector. Low cost alternative is dedicated table top low voltage transmission electron microscope.

Chemical element

A chemical element is a chemical substance that cannot be broken down into other substances. The basic particle that constitutes a chemical element is the atom, and each chemical element is distinguished by the number of protons in the nuclei of its atoms, known as its atomic number. For example, oxygen has an atomic number of 8, meaning that each oxygen atom has 8 protons in its nucleus. This is in contrast to chemical compounds and mixtures, which contain atoms with more than one atomic number.

Spectrometer

A spectrometer (spɛkˈtrɒmɪtər) is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the spectral components are somehow mixed. In visible light a spectrometer can separate white light and measure individual narrow bands of color, called a spectrum. A mass spectrometer measures the spectrum of the masses of the atoms or molecules present in a gas.

Electron diffraction

Electron diffraction refers to changes in the direction of electron beams due to interactions with atoms. Close to the atoms the changes are described as Fresnel diffraction; far away they are called Fraunhofer diffraction. The resulting map of the directions of the electrons far from the sample (Fraunhofer diffraction) is called a diffraction pattern, see for instance Figure 1. These patterns are similar to x-ray and neutron diffraction patterns, and are used to study the atomic structure of gases, liquids, surfaces and bulk solids.

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