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INTERNATIONAL ISO
STANDARD 80000-10
Second edition
2019-08
Quantities and units —
Part 10:
Atomic and nuclear physics
Grandeurs et unités —
Partie 10: Physique atomique et nucléaire
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Bibliography .41
Alphabetical index .42
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www. iso. org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www. iso.o rg/patents).
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.org/iso/foreword. html.
This document was prepared by Technical Committee ISO/TC 12, Quantities and units, in collaboration
with Technical Committee IEC/TC 25, Quantities and units.
This second edition cancels and replaces the first edition (ISO 80000-10:2009), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— the table giving the quantities and units has been simplified;
— some definitions and the remarks have been stated physically more precisely;
— definitions in this document have been brought in line with their equivalent ones in ICRU 85a.
A list of all parts in the ISO 80000 and IEC 80000 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www. iso. org/members. html.
iv © ISO 2019 – All rights reserved
Introduction
0 Special remarks
0.1 Quantities
Numerical values of physical constants in this document are quoted in the consistent values of the
fundamental physical constants published in CODATA recommended values. The indicated values are
the last known before publication. The user is advised to refer to the CODATA website for the latest
values, https: //physics .nist .gov/cuu/Constants/index .html.
h
The symbol is the reduced Planck constant, it is equal to , where h is the Planck constant.
2π
0.2 Special units
1 eV is the energy acquired by an electron in passing a potential difference of 1 V in vacuum.
0.3 Stochastic and non-stochastic quantities
Differences between results from repeated observations are common in physics. These can arise
from imperfect measurement systems, or from the fact that many physical phenomena are subject to
inherent fluctuations. Quantum-mechanical issues aside, one often needs to distinguish between a
stochastic quantity, the values of which follow a probability distribution, and a non-stochastic quantity
with its unique, expected value (expectation) of such distributions. In many instances the distinction
is not significant because the probability distribution is very narrow. For example, the measurement
of an electric current commonly involves so many electrons that fluctuations contribute negligibly to
inaccuracy in the measurement. However, as the limit of zero electric current is approached, fluctuations
can become manifest. This case, of course, requires a more careful measurement procedure, but perhaps
more importantly illustrates that the significance of stochastic variations of a quantity can depend on
the magnitude of the quantity. Similar considerations apply to ionizing radiation; fluctuations can play
a significant role, and in some cases need to be considered explicitly. Stochastic quantities, such as
the energy imparted and the specific energy imparted (item 10-81.2) but also the number of particle
traversals across microscopic target regions and their probability distributions, have been introduced
as they describe the discontinuous nature of the ionizing radiations as a determinant of radiochemical
and radiobiological effects. In radiation applications involving large numbers of ionizing particles, e.g. in
medicine, radiation protection and materials testing and processing, these fluctuations are adequately
represented by the expected values of the probability distributions. “Non-stochastic quantities” such
as particle fluence (item 10-43), absorbed dose (item 10-81.1) and kerma (item 10-86.1) are based on
these expected values.
This document contains definitions based on a differential quotient of the type dA/dB in which the
quantity A is of a stochastic nature, a situation common in ionizing radiation metrology. In these cases,
quantity A is understood as the expected or mean value whose element ΔA falls into element ΔB. The
differential quotient dA/dB is the limit value of the difference quotient ΔA/ΔB for ΔB → 0. In the remarks
of the definitions falling in this category, a reference to this paragraph is made.
INTERNATIONAL STANDARD ISO 80000-10:2019(E)
Quantities and units —
Part 10:
Atomic and nuclear physics
1 Scope
This document gives names, symbols, definitions and units for quantities used in atomic and nuclear
physics. Where appropriate, conversion factors are also given.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
The names, symbols, and definitions for quantities and units used in atomic and nuclear physics are
given in Table 1.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
2 © ISO 2019 – All rights reserved
Table 1 — Quantities and units used in atomic and nuclear physics
Item No. Quantity Unit Remarks
Name Symbol Definition
10-1.1 atomic number, Z number of protons in an atomic nucleus 1 A nuclide is a species of atom with speci-
fied numbers of protons and neutrons.
proton number
Nuclides with the same value of Z but
different values of N are called isotopes
of an element.
The ordinal number of an element in
the periodic table is equal to the atom-
ic number.
The atomic number equals the quo-
tient of the charge (IEC 80000-6) of
the nucleus and the elementary charge
(ISO 80000-1).
10-1.2 neutron number N number of neutrons in an atomic nucleus 1 Nuclides with the same value of N but
different values of Z are called isotones.
N – Z is called the neutron excess number.
10-1.3 nucleon number, A number of nucleons in an atomic nucleus 1 A = Z + N
mass number Nuclides with the same value of A are
called isobars.
10-2 rest mass, m(X) for particle X, mass (ISO 80000-4) of that particle at rest in kg EXAMPLE
an inertial frame
proper mass m u m(H O) for a water molecule, m for an
X 2 e
electron.
Da
Rest mass is often denoted m .
1 u is equal to 1/12 times the mass of a
free carbon 12 atom, at rest and in its
ground state.
1 Da = 1 u
10-3 rest energy E energy E (ISO 80000-5) of a particle at rest: J
0 0
N m
Em= c
00 0
2 −2
kg m s
where
m is the rest mass (item 10-2) of that particle, and
c is speed of light in vacuum (ISO 80000-1)
Table 1 (continued)
Item No. Quantity Unit Remarks
Name Symbol Definition
10-4.1 atomic mass m(X) rest mass (item 10-2) of an atom X in the ground state kg
m(X)
is called the relative atomic mass.
m u
X
m
u
Da
1 u is equal to 1/12 times the mass of a
free carbon 12 atom, at rest and in its
ground state.
1 Da = 1 u
10-4.2 nuclidic mass m(X) rest mass (item 10-2) of a nuclide X in the ground state kg 1 u is equal to 1/12 times the mass of a
free carbon 12 atom, at rest and in its
m u
X
ground state.
Da
1 Da = 1 u
10-4.3 unified atomic mass m 1/12 of the mass (ISO 80000-4) of an atom of the nuclide kg 1 u is equal to 1/12 times the mass of a
u
constant C in the ground state at rest free carbon 12 atom, at rest and in its
u
ground state.
Da
1 Da = 1 u
10-5.1 elementary charge e one of the fundamental constants in the SI system C
(ISO 80000-1), equal to the charge of the proton and oppo-
s A
site to the charge of the electron
10-5.2 charge number, c for a particle, quotient of the electric charge (IEC 80000-6) 1 A particle is said to be electrically neu-
and the elementary charge (ISO 80000-1) tral if its charge number is equal to zero.
ionization number
The charge number of a particle can be
positive, negative, or zero.
The state of charge of a particle may be
presented as a superscript to the symbol
of that particle, e.g.
+ ++ 3+ - -- 3-
H , He , Al , Cl , S , N .
4 © ISO 2019 – All rights reserved
Table 1 (continued)
Item No. Quantity Unit Remarks
Name Symbol Definition
10-6 Bohr radius a radius (ISO 80000-3) of the electron orbital in the hydro- m The radius of the electron orbital in the
gen atom in its ground state in the Bohr model of the atom: H atom in its ground state is a in the
Å
Bohr model of the atom.
4πε
−10
ångström (Å), 1 Å: = 10 m
a =
me
e
where
ε is the electric constant (IEC 80000-6),
is the reduced Planck constant (ISO 80000-1),
m is the rest mass (item 10-2) of electron, and
e
e is the elementary charge (ISO 80000-1)
−1
10-7 Rydberg constant R spectroscopic constant that determines the wave numbers m The quantity R = R hc is called the
∞ y ∞ 0
of the lines in the spectrum of hydrogen: Rydberg energy.
e
R =
∞
8πε ahc
00 0
where
e is the elementary charge (ISO 80000-1),
ε is the electric constant (IEC 80000-6),
a is the Bohr radius (item 10-6),
h is the Planck constant (ISO 80000-1), and
c is the speed of light in vacuum (ISO 80000-1)
Table 1 (continued)
Item No. Quantity Unit Remarks
Name Symbol Definition
10-8 Hartree energy E energy (ISO 80000-5) of the electron in a hydrogen atom eV The energy of the electron in an H atom
H
in its ground state: J in its ground state is E .
H
E
h 2 −2
kg m s
e
E =
H
4πε a
where
e is the elementary charge (ISO 80000-1),
ε is the electric constant (IEC 80000-6), and
a is the Bohr radius (item 10-6)
10-9.1 magnetic dipole μ for a particle, vector (ISO 80000-2) quantity causing a m A For an atom or nucleus, this energy is
moment change to its energy (ISO 80000-5) ΔW in an external mag- quantized and can be written as:
netic field of field flux density B (IEC 80000-6):
W = g μ M B
x
ΔW = −μ · B
where
g is the appropriate g factor (item 10-
14.1 or item 10-14.2), μ is mostly the
x
Bohr magneton or nuclear magneton
(item 10-9.2 or item 10-9.3), M
...