NuDat 3 Glossary
Note: The definitions of some of the terms used in NuDat 3 can be found in this glossary. Users should be aware that many of these terms have different meanings in other scientific and technical areas.
The total number of protons and neutrons in a given nucleus.
For isotopes that occur naturally, the abundance values are proportional to the probability of finding these isotopes and normalized so that the sum of the abundances for all the isotopes of a given chemical element is equal to 100. The source is the "Table of Isotopes", by N. Holden, "The CRC handbook of Chemistry and Physics(2004)".
A 4He nucleus, that is, a nucleus made up of 2 neutrons and 2 protons.
Electrons that are produced when a vacancy in an orbit A is filled by an electron from the orbit B and an electron from an orbit C is ejected. These electrons are labeled by the three orbits that are involved in the production. For instance, AugerKL2L3 means that the original vacancy was in the K orbit, which was filled by an electron in the L2 orbit and the ejected electron came from the L3 orbit. Coster-Kronig transitions are a special type of Auger electrons where the last two orbit are part of the same shell.
Following nuclear decay, vacancies in the electron orbits are produced, which are filled by the emission of X-rays and electrons. Often, instead of listing the energy and intensity for each Auger electron, average intensities and sum intensities are given. For instance, the intensity of the Auger K electrons is the sum of the intensities for all the KBC Auger electrons.
The transformation of one neutron inside a nucleus into a proton plus an electron and an antineutrino:
neutron -> proton + electron + anti-ν
Click here for more information about this decay.
The transformation of one proton inside a nucleus into a neutron plus a positron and a neutrino:
proton -> neutron + positron + ν
Click here for more information about this decay.
β-delayed particle emission
The emission of a nucleon, nucleons or a nucleus following β-decay. For proton rich nuclei, the emission of a proton following β+ decay and electron capture has been observed. For neutron rich nuclei, the release of one or two neutrons following β- decay is possible. The emission of alpha particles has been observed for some nuclei in all types of β decay. Also, for a few nuclei, fission can take place following β+ decay and electron capture.
Conversion electrons (CE)
The electrons emitted during internal conversion. They are labeled by the orbit the electron had occupied prior to the ejection. For instance, CE-L means conversion electron from the L shell. Click here to read more about this topic.
The emission of a nucleus heavier than an α particle, for instance 14C. Branching ratios for this decay tend to be very small, due to the large Coulomb barrier encountered by the cluster and its very small pre-formation factor, that is, the probability of finding the cluster formed inside the nucleus.
A 2H nucleus, that is, a nucleus made up of 1 neutron and 1 proton.
The product of a radiation energy times the probability per disintegration, the resulting unit is MeV×Bq-s.
Double β decay
The simultaneous transformation of two neutrons inside a nucleus into two protons, or alternatively, the simultaneous transformation of two protons into two neutrons.
A negatively charged fundamental particle (lepton). It has a mass of 0.5109989 4 MeV, a charge of -1.60217646×10-19 6 Coulombs and Jπ=1/2+. Electrons bind to atomic nuclei, occupying specific atomic levels.
Electron capture (EC)
The process where one of the protons inside a nucleus following the interaction with one of the orbiting electrons transforms into a neutron plus a neutrino:
proton + electron -> neutron + ν
Click here for more information about this decay.
A word, often in Latin, used to indicate materials with identical chemical properties. There is a one-to-one correspondence between the element name and the number of protons. For instance, all carbon atoms have 6 protons in their nuclei. To read more about element names and the history behind them, click here
End point energy
The maximum kinetic energy that an electron in β- decay or a positron in β+ decay can have, obtained when the kinetic energy of the neutrino/anti-neutrino is equal to zero.
The term "gamma rays" is used here for electromagnetic waves (photons) that have a nuclear origin, that is, photons are emitted following the rearrangement of the protons and neutrons in a nucleus. In contrast, the term "X rays" is used for photons emitted following the rearrangement of the electrons orbiting an atomic nucleus. Gamma rays are one type of radiation.
When a gamma rays is questionable, it will appear as a dashed line in the plots, and a question mark ? will follow the energy value in the list of levels.
Gamma ray emission
Atomic nuclei are quantum system with a discrete set of energies. Gamma ray emission can take place when a nucleus rearranges its protons and neutrons into a lower energy state. Click here to read more about this process.
The length of time for a given radioactive species to reduce its activity in half. The number of decays as a function of time is given as:
N(T)=N0 exp( - ln(2) × (T-T0)/T1/2)
T1/2 is related to the life-time τ by:
T1/2=ln(2) × τ
and to the width Γ by
T1/2= ln(2) × (h/2π) / Γ
where h is Planck's constant.
Please note that when the half-life of a given nuclear level is smaller than 10-15 seconds, it is customary to list the width (Γ) of the level instead.
Radiation intensities are listed throughout <%=link%>. These intensities indicate the probability of observing the corresponding radiations. Two different conventions are used:
- For Decay Radiation, intensities are listed per 100 decays of the parent nucleus. For instance, in the decay of 232Th, the alpha particle with 4012 keV is listed as having an intensity of 78.2 %, which means that this alpha particle will be emitted 78.2 times for every 100 decays of 232Th.
- For the Gamma rays listed in the Adopted Levels, intensities correspond to gamma branching ratios for each level, assigning 100 to the strongest gamma ray.
A process where the transition from one nuclear level to another level in the same nucleus is carried out by transferring the excess energy to an orbiting electron. The alternate process is gamma emission. The electrons are ejected from the atom with an energy equal to the transition energy minus the electron binding energy. These electrons are called conversion electrons and are labeled by the orbit the electron had occupied. For instance, CE-L means conversion electron from the L shell. Click here to read more about this process.
A number of nuclei with the same number of protons plus neutrons are called isobars, such as 144Sm, 144Nd and 144Gd.
A number of nuclei with the same number of neutrons are called isotones, such as 144Sm, 142Nd and 146Gd.
A number of nuclei with the same number of protons are called isotopes, such as 144Sm, 142Sm and 146Sm.
The angular momentum (J) and parity (π) associated with a nuclear level or a particle. For instance, the ground states of nuclei with even number of protons and neutrons have Jπ=0+. The intrinsic J&pi of the proton is equal to 1/2+.
where E0 is the end-point energy for the transition and f(Z,E0) is the Fermi integral. Logft values increase with increasing T1/2, decay probability and E0 values. There is a correlation between the type of transition and its logft value.
The mass of a nucleus with Z proton and N neutrons in a neutral-atom state is:
Mass(Z,N)=Z*Mass(hydrogen atom)+N*Mass(free neutron) - BE(Z,N)
where BE(Z,N) is the Binding Energy, that is, the energy needed to dissociate the nucleus into free nucleons. Note in this product, masses are given in energy units.
The atomic mass unit (amu) is defined so that 1 amu is equal to the mass of a 12C atom divided by 12.
Mass excess (Δ)
The mass excess Δ(Z,N) is defined as:
Δ(Z,N)=( Mass(Z,N) (amu) - A ) × amu
where Mass(Z,N) (amu) is mass in atomic mass units and amu=Mass(6,6)/12. The mass excess as well as many other related quantities can be obtained using QCalc
In the case of mixed-multipolarities gamma rays, the mixing ratio (δ) is a quantity used to indicate the probability of each multipolarity. For instance, if the multipolarity is equal to M1+E2 and the mixing ratio equal to 1, the gamma is 1/(1+δ2)=50% M1 and δ2/(1+δ2)=50% E2.
The angular momentum and parity carried by a gamma ray. The standard notation uses the letters M (magnetic) and E (electric) next to a number to indicate it:
Additionally, the following convention is used:
- If the multipolarity is given as D, it means it is of dipole character, that is M1 or E1.
- Similarly, if it is given as Q, it means quadrupole character, that is M2 or E2.
- If for instance the multipolarity is given as M1+E2, it means that it is M1 mixed with E2.
- If the multipolarity is given in parenthesis, it means that it has not been determined unambiguously. For instance, if it is given as (E2), it means that there is experimental evidence suggesting an E2 character, but we are not 100% sure of the assignment.
- If for instance the multipolarity is given as M1+(E2) or M1(+E2), it means that the multipolarity is mainly M1, but there is experimental evidence of a very small E2 component.
- If the multipolarity is given within square brackets, it means that the multipolarity is deduced from the spins and parities of the initial and final levels. For instance a gamma ray from a 2+ level to a 0+ level whose multipolarity has not been experimentally determined may appear with a multipolarity equal to [E2].
The total number of neutrons in a given nucleus.
An electrically-neutral fundamental particle with Jπ=1/2+. The Greek letter nu (ν) is used to represent them. Neutrinos come in 3 different flavors: electron-, muon-, and tau-neutrinos. The flavor of the neutrino is not fixed as it can change (neutrino oscillations). The mass of the neutrino is known to be very small, but its value is not known. Neutrinos play a crucial role in nuclear physics through beta decay, when a nucleon (neutron or proton) undergoes one of the following transformations:
- β- decay: neutron -> proton + electron + anti-νe
- β+ decay: proton -> neutron + positron + νe
- Electron Capture decay: proton + electron -> neutron + νe
A particle made up of one up quark and two down quarks (udd). It has a mass of 939.56536 8 MeV and Jπ=1/2+. As indicated by their name, neutrons carry zero net electric charge. Together with protons, neutrons are the building blocks of atomic nuclei. Unbound neutrons, that is those that are not inside a nucleus, are unstable, with a half-life of 613.9 6 Seconds. Unbound neutrons undergo the following beta decay: neutron -> proton + electron + anti-ν.
A process where the protons and neutrons in a given nucleus are rearranged into a lower energy state. The transition may involve levels of the same nucleus (gamma emission, electron conversion) or levels of different nucleus (the other types of nuclear decay). Each different process is known as a 'decay mode'.
- Gamma emission, electron conversion
- β- decay
- β+ decay
- Electron Capture (EC)
- β-delayed particle emission
- Double β decay
- Proton decay
- Alpha decay
- Cluster decay
- Spontaneous Fission (SF)
The greek letter epsilon (ε) is often used to indicate the combination of Electron Capture and β+ decay.
The probability of undergoing a given nuclear decay is often indicated using the percent sign followed by the decay mode name and the probability per 100 decays. For instance, %β-=100 means 100% probability of β- decay. The energy released during the decay is called 'Q-value'. For a given decay mode to have a probability larger than 0, the Q-value has to be positive.
Atomic nuclei are quantum systems, that is among other things, that they can not have any value of energy, but only a finite number that depends solely on its number of protons and neutrons. The state associated with a given energy value is known as a nuclear level. The lowest energy level is known as the ground state while the other states are known as excited states. Each level has a number of properties associated with it, such as half-life (T1/2), angular momentum and parity (Jπ) and decay modes.
The following table with examples can help clarify the convention we use for Jπ.
|0+||The spin and the parity were unambiguously determined to be 0 and positive, respectively|
|0||The spin was unambiguously determined to be 0, but the parity could be positive or negative|
|0(+)||The spin was unambiguously determined to be 0, there is evidence for a positive parity, but we are not 100 % sure|
|(0+)||There is evidence for a zero spin and a positive parity, but we are not 100 % sure|
|1,2+||We are sure that the spin and parity are either 1+ or 1- or 2+|
|(1,2+)||We think that the spin and parity are either 1+ or 1- or 2+, but we are not 100% sure|
|4 to 6||We are sure that the spin is either 4 or 5 or 6|
|GE 6||We are sure that the spin is larger than or equal to 6|
When a level is questionable, it will appear as a dashed line in the plots, and a question mark ? will follow the energy value in the list of levels.
Atomic nuclei are made up of protons and neutrons. The letters Z and N are used indicate the number of protons and the number of neutrons, respectively. The letter A is used for the sum of the number of protons and neutrons, that is, A=Z+N. The number of protons can also be specified by the element name. For instance, all nuclei with Z=6 are called "carbon" nuclei, and alternatively, all carbon nuclei have Z=6. An abbreviation of the element name, for instance C for carbon, is known as the chemical symbol.
A given nucleus is uniquely specified by its number of protons (Z) and neutrons (N). To name a nucleus, we use the A (Z+N) value followed by the element name. For instance, 16O means a nucleus with Z=8 and A=16, and therefore N=8. Furthermore, we often write A as a superscript: 16O.
Many other methods have been implemented to name nuclei, for instance, 16-O and O-16 also refer to the Z=8 and A=16 nucleus. Some applications use 8016=Z*1000+A to name the same nuclei, which has the advantage that it is a numerical expression. Finally, some methods provide more than the minimal amount of information needed, such as '8-O-16'.
Isobars, Isotones and Isotopes
Nuclei with the same A number (total number of protons plus neutrons) are called Isobars. Nuclei with the same N number (total number of neutrons) are called Isotones, and nuclei with the same Z number (total number of protons) or same chemical element are called Isotopes.
The electron antiparticle, having the same mass and spin as the electron but opposite electric charge. When an electron and a positron meet, they annihilate, emitting 2 gamma rays of 511 keV each.
A particle made up of two up quarks and one down quark (uud). It has a mass of 938.27203 8 MeV, and Jπ=1/2+. Together with neutrons, protons are the building blocks of atomic nuclei. Unlike neutrons, free protons are stable.
The mass difference in energy units between an initial and a final nuclear configuration. Decay Q-values give the energy released in a given nuclear decay, a positive value means that the decay is possible. Reaction Q-values measure the energy released or taken by the reaction. The code Qcalc can be used to obtain numerical values.
The stream of particles released during nuclear decay. The neutrinos emitted in β decay will not deposit their kinetic energy in the surrounding media due to their negligible interaction probability with matter. The remaining particles, such as photons, electrons, positrons, neutrons, protons, alphas, etc, will do so. This second group is known as "ionizing radiation" as they will knock out electrons from the atoms they interact with. Radiation is often classified by the type of particle: Electromagnetic (gamma rays, x-rays and the 511 keV annihilation peak), light particles (electrons, positrons, conversion and Auger electrons), and heavy particles (neutrons, protons, alphas, cluster nuclei, fission fragments, recoil nuclei).
For a nucleus with Z protons and N neutrons, the proton separation energy measures the energy needed to remove a proton:
where BE is the binding energy. Similarly, the neutron separation energy is:
A 3H nucleus, that is, a nucleus made up of 2 neutron and 1 proton.
The uncertainties listed are typically 1-sigma values, unless otherwise stated. The uncertainties can be expressed in the so-called Nuclear Data Sheets style, or in a standard style. The Nuclear Data Sheets style has been used for a long time since it facilitates data storage, which was crucial in the early days of computing. A table with a brief explanation of the Nuclear Data Sheet style is given below:
|4.623 3||means 4.623 + - 0.003 (standard style)|
|4.6 h 12||means 4.6 + - 1.2 hours (standard style)|
|5.4×103 2||means 5400 + - 200 (standard style)|
|4.2 +8-10||means 4.2 + 0.8 - 1.0 (standard style)|
|-4.2 +8-10||means -4.2 + 0.8 - 1.0 (standard style)|
|9.22 SY||means that the 9.22 value was obtained following some sort of systematic study|
|9.22 Syst||means that the 9.22 value was obtained following some sort of systematic study|
|9.22 CA||means that the 9.22 value is not an experimental one, but the result of a theoretical calculation|
|9.22 2 ?||means that the 9.22 value is questionable|
|9.22 2 S||means that the 9.22 value is an expected value that has not been observed|
An electromagnetic wave (photon) that originates when an electron vacancy is filled by an electron from a higher orbit. Typically, X-rays have energies smaller than 100 keV. X rays are one type of radiation.
There are two conventions to label X-rays, IUPAC and Siegbahn. IUPAC labels X-rays by the initial and final orbits. For the most intense K X-rays, the labels for the two conventions is given in the table below:
The individual L X-rays are not listed. Instead, the average energy and the sum intensity for all the L X-rays is given. Higher-shell X-rays, such as M and N X-rays, are not listed, mainly because of concerns on the uncertainty of the intensities. Also, these X-rays will have considerable less energy than the K and L X-rays.
The total number of protons in a given nucleus.
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