Characteristic x-ray
Encyclopedia
A high energy electron
interacts with a bound electron
in an atom
and ejects it. The incident electron is scattered and the target electron gets displaced from its shell. The incident electron energy must exceed the binding energy
of the electron
to eject it. After the electron has been ejected the atom is left with a vacant energy level
.
This vacant energy level if it occurs in the inner electron levels is called a core hole. This vacancy is subsequently filled by an electron from a higher energy level with the emission of a characteristic x-ray
photon. The characteristic x-ray photon has an energy that corresponds exactly to the difference in energy between the energy level that is vacant and the energy level from which an electron falls.
The x-ray energy is characteristic of the atom that had the core hole and can be used to identify the atom. This is used in various techniques, including X-ray fluorescence spectroscopy, Energy dispersive X-ray spectroscopy and Wavelength dispersive X-ray spectroscopy
. These are used in mineral analysis and elsewhere.
The characteristic-x-ray can be immediately reabsorbed by an electron in the same atom and instead the energy of the characteristic x-ray is given entirely to this electron which is called an Auger electron
. This is like an internal photo-electric effect that occurs after the initial photo-electric effect.
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
interacts with a bound electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
in an atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
and ejects it. The incident electron is scattered and the target electron gets displaced from its shell. The incident electron energy must exceed the binding energy
Binding energy
Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...
of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
to eject it. After the electron has been ejected the atom is left with a vacant energy level
Energy level
A quantum mechanical system or particle that is bound -- that is, confined spatially—can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy levels...
.
This vacant energy level if it occurs in the inner electron levels is called a core hole. This vacancy is subsequently filled by an electron from a higher energy level with the emission of a characteristic x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
photon. The characteristic x-ray photon has an energy that corresponds exactly to the difference in energy between the energy level that is vacant and the energy level from which an electron falls.
The x-ray energy is characteristic of the atom that had the core hole and can be used to identify the atom. This is used in various techniques, including X-ray fluorescence spectroscopy, Energy dispersive X-ray spectroscopy and Wavelength dispersive X-ray spectroscopy
Wavelength dispersive X-ray spectroscopy
The Wavelength dispersive X-ray spectroscopy is a method used to count the number of X-rays of a specific wavelength diffracted by a crystal. The wavelength of the impinging x-ray and the crystal's lattice spacings are related by Bragg's law and produce constructive interference if they fit the...
. These are used in mineral analysis and elsewhere.
The characteristic-x-ray can be immediately reabsorbed by an electron in the same atom and instead the energy of the characteristic x-ray is given entirely to this electron which is called an Auger electron
Auger electron
The Auger effect is a physical phenomenon in which the transition of an electron in an atom filling in an inner-shell vacancy causes the emission of another electron. When a core electron is removed, leaving a vacancy, an electron from a higher energy level may fall into the vacancy, resulting in...
. This is like an internal photo-electric effect that occurs after the initial photo-electric effect.