Nuclear and Particle Physics Topics

1.054571596e-34 J s
Dirac′s constant, also known as h bar.
1.0973731568549e7m-1
Rydberg Constant.
1.60217733e-19 J
Electron Volt.
1.602e-19 C
Electron charge.
1.672e-27kg
Proton mass.
1.759e11Ckg-1
Electron charge to mass ratio.
1836.1526675
Proton to electron mass ratio.
3.289841960368e15 Hz
Rydberg Constant multiplied by the speed of light.
4.13566727e-15 eV s
Plancks Constant.
6.58211889e-16 eV s
Known as h bar or Dirac′s constant.
6.626e-34 Js
Planck′s constant.
9.109e-31 kg
Electron rest mass.
Antiatom
An atom of antimatter.
Antibaryon
The antiparticle of a baryon.
Antibonding Orbital
A molecular orbital that can be described as the result of destructive interference of atomic orbitals on bonded atoms.
Antielectron
The anti particle of an electron.
Antilepton
The antiparticle of a lepton.
Antimatter
Material made from antifermions. We define the fermions that are common in our universe as matter and their antiparticles as antimatter.
Antineutrino
The antiparticle of a neutrino.
Antineutron
The antiparticle of the neutron.
Antinucleon
Antiproton or an antineutron.
Antiparticle
A subatomic particle with the same-size properties as those of the particle although some may have the opposite sign.
Antiproton
The antiparticle of the proton.
Antiquark
The antiparticle of a quark.
Anyon
An elementary particle or particle-like excitation having properties intermediate between those of bosons and fermions.
Atom
The smallest particle of an element that can exist and still retain the ordinary chemical properties of that element.
Atomic Mass Unit
Defined as one twelfth of the mass of the most abundant isotope of carbon (12C)
Atomic Nucleus
A tiny, incredibly dense positively charged mass at the heart of the atom - normally abbreviated Nucleus.
Atomic Number
The atomic number (Z) of an element is the number of protons each atom of that element has in its nucleus.
Atomic Orbital
A wavefunction that describes the behavior of an electron in an atom.
Atomic Packing Factor
The fraction of the volume of a unit cell that is occupied by ′hard sphere′ atoms or ions.
Atomic Particle
One of the particles of which an atom is constituted.
Atomic Radius
One half the distance between nuclei of atoms of the same element, when the atoms are bound by a single covalent bond or are in a metallic crystal.
Atomic Theory
An explanation of chemical properties and processes that assumes that tiny particles called atoms are the ultimate building blocks of matter.
Atomic weight
The weighted average mass of the atoms in a naturally occurring element.
Backscattered Electron
Produced by an incident electron colliding with an atom in the specimen which is nearly normal to the incident′s path.
Band
A set of closely spaced energy levels in an atom, molecule, or metal.
Band Gap Energy
For semiconductors and insulators, the energies that lie between the valence and conduction bands.
Bandgap
The range of energies between existing energy bands where no energy levels exist.
Baryon
A particle with spin 1/2 (or 3/2) which consists of three elementary particles known as quarks.
Baryon Number
A quantum number assigned to elementary particles.
Beta Decay
Radioactive process in which a beta particle is emitted from the nucleus of an atom.
Beta Particle
An electron emitted by a radioactive nucleus.
Beta Ray
A stream of beta particles.
Betatron
An accelerator in which electrons are accelerated to high energies by an electric field produced by a changing magnetic field.
Bevatron
An accelerator in which protons are raised to energies of several billion electron-volts by modulating the frequency of the accelerating voltage.
Bohr Atom
A model of the atom that explains emission and absorption of radiation as transitions between stationary electronic states in which the electron orbits the nucleus at a definite distance.
Bosons
Particles which do not obey the Pauli exclusion principle, for example, photons.
Bound State
This is a state in which a particle is confined within a composite system.
Carrier Particle
A fundamental boson associated with quantum excitations of the force field corresponding to some interaction.
Charge Conservation
The observation that electric charge is conserved in any process of transformation of one group of particles into another.
Charged Particle Beam
A projected stream of charged particles.
Charged Particles
Particles with positive or negative charge, for example electrons, protons or ions.
Charmed Quark
The quark having electric charge 2/3 times the elementary charge and charm C = +1. It is more massive than the up, down, and strange quarks.
Classical Electron Radius
A classical distribution of charge totalling the electron′s charge has electrostatic potential energy equivalent to the electron′s rest mass if it were confined to a volume of this radius.
Closed Shell
A shell that contains the maximum number of electrons permitted by the exclusion principle.
Collision
An encounter between two ojects that changes their existing momentum and energy conditions.
Collision Diameter
The distance between the centres of two colliding molecules when at their closest point of approach.
Collision Frequency
The average number of collisions that a molecule undergoes each second.
Colour Charge
The charge associated with strong interactions.
Convergent Beam Electron Diffraction
An electron probe is tightly focused on a specimen and the resulting pattern of diffracted electrons is observed.
Core Electron
Electrons occupying completely filled shells under the valence shell.
Covalent Bond
Describes the mutual electrostatic attraction of two or more adjacent nuclei for a shared pair of electrons which occupy the same molecular energy level.
Covalent Radius
The radius of atoms obtained from covalent bond lengths.
Dose Equivalent
Parameter used to express the risk of the deleterious effects of ionization radiation upon living organisms.
Dose Rate
A measure of the dose delivered per unit time.
Down Quark
The second flavour of quark (in order of increasing mass), with electric charge -1/3.
Electromagnetic Interaction
The interaction due to electric charge; this includes magnetic effects that have to do with moving electric charges.
Electron
The electron charge is 1.602x10-19 C
Electron Affinity
The measure of an atom′s tendency to gain an electron.
Electron Beam
The stream of electrons generated by the electron gun and accelerated by the accelerator guide.
Electron Capture
A decay process in which an inner atomic electron is captured by the nucleus.
Electron Channelling Patterns
A pattern formed by the periodic backscattering of electrons by the specimen lattice in a SEM.
Electron Charge
e = 1.602x10-19 C
Electron Configuration
A list showing how many electrons are in each orbital or subshell.
Electron Flow
The direction in which electrons flow. This is from negative to positive - as electrons are negatively charged.
Electron Gun
An electrode of a CRT that is equivalent to the cathode and control grid of conventional tubes.
Electron Microscope
A type of microscope that uses a particle beam of electrons to illuminate the specimen and produce a magnified image.
Electron Orbital Movement
The movement of an electron around the nucleus of an atom.
Electron Shell
A group of electrons which have a common energy level that forms part of the outer structure of an atom.
Electron Spin
Electrons have an intrinsic angular momentum that is similar to what would be observed if they were spinning.
Electron Spin Pair
Two electrons with opposite spins, usually occupying the same orbital.
Electron Volt
Unit of energy of moving particles. Given by the kinetic energy acquired by an electron losing one volt of potential.
Electronegativity
Measure of a substances' ability to attract electrons.
Electronic Structure
The distribution of electrons in the material and the energies related to changes in this distribution.
Electron-Positron Annihilation
When an electron and its anti-particle, a positron, collide, they annihilate emitting a pair of gamma-ray photons each with an energy of 511 keV.
Electrovalence
The valence as determined by the electrons lost or gained by the elements reacting to form a compound.
Elementary Particles
The particles which form the building blocks of atoms and those which carry energy.
Energy Band
A collection of closely spaced energy levels.
Excited State
Atom with an electron in a higher energy level than it normally occupies.
Exclusion Principle
No two electrons can have the same set of quantum numbers. This statement also applies to protons, neutrons, and other baryons.
Fermi Level
Energy level at which the probability of finding an electron is one-half.
Fermions
Fermions are particles that satisfy the Pauli exclusion principle and obey the Fermi-Dirac statistics of statistical mechanics.
Fixed-Target Experiment
An experiment in which the beam of particles from an accelerator is directed at a stationary (fixed) target. The target may be a solid, a tank containing liquid or gas, or a gas jet.
Free Electron
Electron which is not attached to a nucleus.
Fundamental Particle
A particle with no internal substructure.
Gamma Rays
Gamma rays are electromagnetic waves or photons emitted from the nucleus (centre) of an atom.
Geiger Counter
A radiation detector consisting of two electrodes with a low-pressure gas in between.
Ground State
The lowest energy state of a system allowed by quantum mechanics.
High-Intensity Gamma
A level a gamma radiation flux on the order of 10E4 roentgens or higher.
Induced Radioactivity
Radioactivity produced in materials, especially metals, exposed to high-energy photons or neutrons.
Linac
An abbreviation for linear accelerator.
Linear Accelerator
Particle accelerator in which charged particles are accelerated in a straight line, either by a steady electrical field or by means of radiofrequency electric fields.
Muon Chamber
The outer layers of a particle detector capable of registering tracks of charged particles.
Neutral Particle Beam
A projected stream of neutral particles such as deuterium or heavy hydrogen at very high particle energies and low currents.
Neutron
A sub-atomic particle, within the nucleus of an atom, which has unit mass and zero charge.
Non-Ionizing Radiation
Radiation without enough energy to remove tightly bound electrons from their orbits around atoms.
Nuclear and Particle Physics Books
Lists all Particle Physics Books in the Encyclopaedia
Nuclear and Particle Physics Calculations
Lists all Particle Physics Calculations in the Encyclopaedia
Nuclear and Particle Physics Conversions
Lists all Particle Physics Conversions in the Encyclopaedia
Nuclear and Particle Physics Weblinks
Lists all Particle Physics Weblinks in the Encyclopaedia
Particle Accelerator
A device for accelerating charged particles to high velocities.
Particle Beam
A stream of particles guided into a defined direction by a particle accelerator.
Pauli Exclusion Principle
No two electrons can have the same set of quantum numbers.
Photoelectron
An electron ejected from an atom or molecule that has absorbed a photon.
Prompt Neutrons
Those neutrons released coincident with the fission process, as opposed to the neutrons subsequently released.
Proton
The central nucleus of an atome is formed from protons and neutrons. The nucleus of a hydrogen atom has a single proton.
Proton-Proton Chain
In the Sun and other less massive stars, this chain is the primary source of heat and radiation.
Quark
A constituent of hadrons. Quarks come in six flavors and three colors each.
Quark Theory of the Structure of Matter
The theory that all hadrons, such as the protons and neutrons in the nucleus, are made of quarks.
Radiation Barrier
Radiation-absorbing material, such as lead or concrete, used to reduce radiation exposure.
Radiation Transport
The field of nuclear science dealing with the prediction and measurement of the movement of electromagnetic radiation or particles through matter.
Radionuclide
Materials that produce ionization radiation, such as X-rays, gamma rays, alpha particles, and beta particles.
Residual Interaction
Interaction between objects that do not carry a charge but do contain constituents that have that charge.
Secondary Electron
Produced by an incident electron passing near an atom in the specimen, near enough to impart some of its energy to a lower energy electron, usually in the K-shell.
Selected Area Electron Diffraction
An aperture is used to define the area from which a diffraction pattern is formed in a TEM specimen.
Shell
A surface made of thin material.
Shells
Where the electrons generally stay.
Shielding
Technique designed to minimize internal and external interference.
Solar Protons
Protons emitted by the sun, especially during solar flares.
Specimen Interaction
Reactions that occur inside the specimen when being struck with a beam of energetic electrons.
Specimen Interaction Volume
The volume inside the specimen in which all specimen interactions occur during electron beam irradiation.
Spin
The name given to the angular momentum carried by a particle.
Stable
In nuclear physics if something is stable it means it does not decay.
Standard Model
Physicists' name for the theory of fundamental particles and their interactions.
Storage Ring
A circular structure in which either high energy electrons and/or positrons, or protons and/or antiprotons are circulated many times before being used in collisions.
Strange Particle
A particle with a nonzero value of strangeness.
Strange Quark
The third flavour of quark, in order of increasing mass, with electric charge -1/3.
String Theory
A theory of elementary particles incorporating relativity and quantum mechanics in which the particles are viewed not as points but as extended objects.
Strong Interaction
The interaction responsible for binding quarks and gluons to make hadrons.
Subatomic
Smaller than the atom. The structure of the atom.
Subatomic Particle
Any particle that is small compared to the size of the atom.
Subshell
A set of electrons with the same azimuthal quantum number.
Tau Lepton
The third flavor of charged lepton (in order of increasing mass), with electric charge -1.
Thermoelectron
An electron emitted by a very hot object.
Top Quark
The sixth flavor of quark, in order of increasing mass, with electric charge +2/3.
Trivalent Impurity
Acceptor impurities containing only three valence electrons.
Uncertainty Principle
The quantum principle, first formulated by Heisenberg, that states that is is not possible to know exactly both the position x and the momentum p of an object at the same time.
Unpaired Electron
A single electron occupying an orbital.
Unstable
Characteristic of a structure that collapses or deforms under a realistic load or a chemical that decomposes.
Up Quark
The first flavor of quark, in order of increasing mass, with electric charge +2/3.
Vacuum Zero
The energy of an electron at rest in empty space, used as a reference level in energy band diagrams.
Valence
The charge on an ion based on the number of electrons transferred or shared within a specific structure.
Valence Band
Highest filled or almost filled band in a semiconductor.
Valence Electrons
The electrons in the outermost shell of an atom.
Valence Shell
The electrons in the outermost shell of an atom.
Valence Shell Electron Pair Repulsion Theory
A model that explains the shapes of molecules by assuming that electron pairs arrange themselves around atoms in a way that minimizes electron-electron repulsions.
Virtual Particles
Particles that exist only for the brief moment allowed by Heisenberg′s uncertainty principle.
Wave Particle Duality
The observation that electrons; photons; and other very small entities behave like particles in some experiments and like waves in others.
Weak Interaction
The interaction responsible for all processes in which flavour changes, hence for the instability of heavy quarks and leptons, and particles that contain them.
W Particles
Together with the electrically neutral Z particle, are the carriers of the electroweak force.
Z Particle
A carrier particle of weak interactions. It is involved in weak processes that do not change flavour.

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Subjects: Physics