Alpha
particles
following the beta decay.
Bremsstrahlung 
X-rays produced when fast
electrons pass through
matter. The bremsstrahlung (German for "slowing-down radiation")
energy varies from 0 to the energy of the electron.
Carbon-Nitrogen-Oxygen
Cycle (see also hot CNO
cycle)
In stars more massive than the sun (>1.1 Solar masses), this
cycle is the primary process which converts hydrogen into helium.
12C serves as a catalyst, an ingredient which is
necessary for the reaction but is not consumed.
Listing
of the steps
Compton
Scattering
Collision process between a gamma
ray and a bound atomic electron
where only part of the gamma-ray energy is transferred to the
electron. The probability for Compton
scattering is approximately proportional to Z, and for energies
greater than 500 keV approximately proportional to
1/Egamma
Conversion Electron
An alternate process to x-ray
emission during the de-excitation of an excited atom.
Decay Branching %
The nuclide decay rate by a particular decay mode. Some
nuclides decay by only one mode (100%), and others by more than
one mode. For example, 187Pb decay by beta
decay (98%) and alpha decay
(2%).
Decay Mode
Disappearance of a radioactive substance due to nuclear
emission of an alpha or
beta particle, capture
of an atomic electron,
neutrinos, spontaneous
fission, and the emission of bremsstrahlung,
x-rays, and conversion
electrons. In rare instances proton,
neutron, or light element
(for example 14C) emission can occur. When a large
amount of decay energy is available, beta-delayed
emission of neutrons, protons, and other particles may occur.
Decay
Scheme
A drawing depicting the decay of a parent nucleus
to a daughter nucleus. The
betas or alphas
are shown as arrows from the parent level to daughter level(s).
Gamma rays de-exciting
daughter levels are shown on the decay scheme.
Electromagnetic radiation
Radiation consisting of electric and magnetic waves that
travel at the speed of light. Examples: light, radio waves,
gamma rays, x-rays.
Electron
An elementary particle with a unit electrical charge and a
mass 1/1837 of the proton.
Electrons surround the atom's positively charged nucleus
and determine the atom's chemical properties. In our diagrams, an
electron is represented by this: 
Electron
Capture Decay
Nuclear decay by capture of an atomic electron.
If the decay energy is greater than 1022 keV, positron
emission can also occur in competition with electron
capture.
Energy Scale
The energy scale used by most nuclear scientists is electron
volts (eV), thousands of electron volts (keV), and millions of
electron volts (MeV). An electron volt is the energy acquired when
an electron falls through a
potential difference of 1 volt. 1 eV=1.602*1012ergs.
Masses are also given by their "mass-equivalent" energy
(E=mc2). The mass of the proton
is 938.27231 MeV.
E=mc2
Where: e is energy, m is mass, and c is the speed of
light. Einstein's famous equation describes how energy and mass
are related. In our animated decays, mass is lost. That mass is
converted into energy in the form of electromagnetic
waves. Because the speed of light is so great, a little matter
can transform into large amount of energy.
ENSDF
The Evaluated Nuclear Structure Data File is evaluated by an
international collaboration of nuclear scientists. ENSDF is a
database of nuclear structure and decay data.
Gamma
Rays
A highly penetrating type of nuclear radiation, similar to x-rays
and light, except that it comes from within the nucleus
of an atom, and, in general, has a shorter wavelength. Gamma rays
emission is a decay mode by which excited state of a nucleus
de-excite to lower (more stable) state in the same nucleus.
In our diagrams, a gamma ray is represented by this: 
Geiger Counter
A radiation detector consisting of two electrodes with a
low-pressure gas in between. A voltage is maintains such that if
radiation passing through the counter ionizes the gas, an
avalanche of electrons will
occur. Geiger counters can count radiation but cannot distinguish
either the energy or kind of radiation.
Ground State
A lowest energy state of the nucleus.
Half-Life
Used to measure the rate of radioactive decay of disintegration.
The time lapse during which a radioactive mass loses one half of
its radioactivity.
Helium
Burning (triple alpha process)
When temperature in the core of a star reaches 100 million
degrees, three colliding helium nuclei fuse to form a carbon
nucleus. This process occurs when the star is a red giant.
Hot
Carbon-Nitrogen-Oxygen Cycle (see
also C-N-O cycle)
Complete
Listing of the
Steps
Hydrogen
Burning
Hydrogen burning is the fusion of four hydrogen nuclei
(protons) into a single helium nucleus (two protons and neutrons.)
The process is a series of reactions. The type of reactions depend
on the mass of a star and its core temperature and density. In our
Sun, the process is a proton-proton chain. In more massive stars,
the C-N-O cycle (Carbon-Nitrogen-Oxygen)
serves to fuse hydrogen into helium.
Intensity Branching(%)
The intensity of a radiation emitted during radioactive
decay.
Isobars
Nuclides of the same
atomic mass but different atomic
number.
Isomers
A long-lived excited state of the nucleus.
Arbitrarily defined in as the Table
of Isotopes as having a half-life greater than 1 ms.
Isotopes
Two or more nuclides having the same atomic
number, thus constituting the same element, but differing in
the mass number. Isotopes of a given element have the same number
of nuclear protons but
differing numbers of neutrons.
Naturally occurring chemical elements are usually mixtures of
isotopes so that observed (non-integer) atomic weights are average
values for the mixture.
Mass Number
The sum of the number of neutrons
and protons in a nucleus.
Natural Abundance
Percentage of an element occurring on earth in a particular stable
isotopic form.
Neutrino
An electrically neutral particle with negligible mass. It is
produced in many nuclear reactions such as in beta
decay. In our diagrams, it is represented by this: 
Neutron
One of the basic particles which make up an atom. A neutron and a
proton have about the same
weight, but the neutron has no electrical charge. In our diagrams,
a neutron is represented by this: 
Neutron Decay
Nuclear decay by emission of a neutron.
Neutron-Induced
Fission
Bombardment with a neutron
resulting in splitting the nucleus
into two parts (fission fragments), neutrons,
and gamma rays.
Neutron-induced fission movie by Encylopedia Brittanica
Neutron Separation Energy
The energy required to remove a neutron
from a nucleus.
Nuclear
Reaction
Reaction between an energetic incident projectile (neutron,
proton, or nucleus
) from a reactor or particle accelerator and a target
nucleus producing product
nuclides, gamma rays,
particles, and other radiations.
Particle
Transfer
Nucleon
A proton or neutron.
Nucleus
The core of the atom, where most of its mass and all of
its positive charge is concentrated. Except for hydrogen, it
consists of proton and
neutrons.
NSR
The Nuclear Science Reference file is a compilation of about
160,000 references relevant to nuclear structure and decay.
Pair
Production
A collision process for gamma
rays with energies greater than 1022-keV (two electron
masses) where an electron
/positron pair is produced. A heavy nucleus must be present
for pair production. For high-energy gamma
rays the pair production process is proportional to
Z2 and ln(gamma).
Parity
A nucleus or particle has
odd (-) or even (+) parity according to whether or not its wave
function changes sign when all of the space coordinates are
changed.
Photoelectric
effect
Collision process between an x-ray
or gamma rays and a bound
atomic electron where the
photon disappears, the bound electron is ejected, and the incident
energy is shared between the ejected electron and the remaining
atom. The photon energy must be greater than the atomic binding
energy. The probability for the photoelectric effect is
approximately proportional to Z5 of the absorber and
falls of by about E(gamma)3.5.
Positron
Annihilation
Positron decay in matter by annihilation with an electron.
Usually and "atom" of positronium (e+e-) forms which annihilates
to produce two 511-keV photons. Occasionally, the positron will
annihilate in flight to produce on or more photons sharing the
total rest mass and kinetic energy of the positron and electron.
Proton
One of the basic particles which makes up an atom. The proton is
found in the nucleus and has
a positive electrical charge equivalent to the negative charge of
an electron and a mass
similar to that of a neutron.
A proton is a hydrogen nucleus.
In our diagrams, a proton is represented by this: 
Proton-Proton Chain
In the Sun and other less massive stars, this chain is the
primary source of heat and radiation. The proton-proton chain
converts hydrogen into helium releasing energy in the form of
particles and gamma-rays. Hydrogen is
converted into helium in a chain of reactions. The first reaction
takes an average of 1 billion years to occur while the others are
much shorter. One step is only 1 second long. In the Sun, there
are so many hydrogen nuclei that the 1 billion year waiting period
does not stop it from producing tremendous radiation.
List
of the steps
Proton Separation Energy
The energy required to remove a proton from a nucleus.
Proton
Decay
Nuclear decay by emission of a proton.
Q-value
The energy available for decay. This energy is released by the
nucleus mainly as gammas,
betas, neutrinos,
and/or alpha particles.
Scintillation
Counter
A scintillation counter consists of a material that emits light
when radiation passes through it. Various liquid, plastic, and
crystalline materials have scintillation properties. Scintillation
light is measured with photomultiplier tubes. In general the
amount of scintillator light detected is proportional to the
energy of the radiation.
Semiconductor Detector
Radiation striking very pure Ge and Si semiconductor detectors
can excite a large number of electrons
into the conduction band leading to a measurable current. This
current is proportional to the energy of the radiation.
Semiconductor detectors can be used to accurately measure the
energy and intensity of radiation.
Spin
Used to describe the angular momentum of the nucleus.
Spontaneous
Fission
Nuclear decay by splitting the nucleus
into two parts (fission fragments), neutrons,
and gamma rays.
Triple Alpha Process (see helium
burning)
X-rays
A type of radiation of higher frequency (or energy) that
visible light but lower that gamma
rays. Usually produced by fast electrons
going through matter or by the de-excitation of excited atoms. In
our diagrams, a x-ray is represented by this: 
*The background image is a chart of the nuclides. Each box
represents an nuclide. The neutron numbers increase to the right
on the x-axis and the proton number increases vertically in the
y-axis. Each color represents different decay modes.
The white band in the middle is for stable nuclides.
The nuclides farther from the stable band are more unstable.
Astrophysics
Glossary
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Isotopes