Table 7.5 -- EUs whose label begins with A-L

Label Symbol Quantity Definition EQ label Code References
AMP_PER_METRE A/m lineic electric current (linear electric current density) The electric current in a conducting sheet divided by the width of the sheet. LINEIC_ELECTRIC-
_CURRENT		 1 [I31-5, 5-16.a]
magnetic field strength A vector quantity, the rotation (curl) of which is equal to the sum of the electric current density and the time derivative of the electric flux density. [I31-5, 5-17.a]
magnetization The extent to which a magnetic material is magnetized, given by the magnetic moment per unit volume. [I31-5, 5-28.a]
AMP_PER_SQ_M_KELVIN_SQD A/(m2 · K2) thermionic emission current density A vector quantity, the integral of whose normal component over a heated surface is equal to the net number of particles (electrons or ions) emitted from that surface, as a function of the thermodynamic temperature of that surface. THERMION_EMISSION-
_CUR_DENS		 2 [I31-13, 13-27.a]
AMP_PER_SQ_METRE A/m2 areic electric current (electric current density) A vector quantity, the integral of whose normal component over a given surface is equal to the electric current flowing through that surface. AREIC_ELECTRIC-
_CURRENT		 3 [I31-5, 5-15.a]
AMPERE A current linkage The net electric conduction current through a closed loop. ELECTRIC_CURRENT 4 [I31-5, 5-18.a]
electric current That constant electric current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per metre of length.
SI base unit.		 [I31-0, Table 1],
[I31--5, 5-1.a]
magnetic potential difference On a given path, the magnetic potential difference between point 1 and point 2 is the line integral from 1 to 2 of the magnetic field strength along that path. [I31-5, 5-18.a]
magnetomotive force The work required to carry a magnetic pole of unit strength once around a magnetic circuit. [I31-5, 5-18.a]
BECQUEREL Bq activity of a radio nuclide The average number of spontaneous nuclear transitions from a particular energy state occurring in an amount of a radio nuclide in a small time interval, divided by that interval.
1 Bq = 1 s-1.		 RADIONUCLIDE-
_ACTIVITY		 10 [I31-0, Table 3],
[I31-9, 9-33.a],
[I31-10, 10-49.a]
BECQUEREL_PER_CUBIC_METRE Bq/m3 volumic activity (activity concentration) Activity (of a radio nuclide) divided by the total volume of the sample. VOLUMIC_ACTIVITY 11 [I31-9, 9-35.a]
BECQUEREL_PER_KG Bq/kg massic activity (specific activity) Activity of a radio nuclide divided by the total mass of the sample. MASSIC_ACTIVITY 12 [I31-9, 9-34.a]
BEL B field quantity ratio (level difference) Twice the common logarithm of a field quantity ratio.
1 B is the level of a field quantity when 2 lg (F/F0) = 1 where F and F0 represent two amplitudes of the same kind, F0 being a reference amplitude.
1 B = (1/2) ln 10 Np = 1,151 293 Np (approximately).		 FIELD_OR_POWER-
_LEVEL_DIFF		 13 [I31-2, 2-9.b]
power quantity ratio (level difference) The common logarithm of a power quantity ratio.
1 B is the level of a power quantity when lg (P/P0) = 1 where P and P0 represent two powers, P0 being a reference power.		 [I31-2, 2-10.b]
sound power level LW = 1/2 ln (P/P0) = 1/2 ln 10·lg (P/P0) where P is the root-mean-square of the sound power and the reference power p0 = 1 x 10-12 W. [I31-7, 7-22.a]
sound pressure level Lp = ln (p/p0) = ln 10·lg (p/p0) where p is the root-mean-square value of the sound pressure and the reference pressure p0 = 20 μPa. [I31-7, 7-21.a]
CANDELA cd luminous intensity The luminous intensity, in a given direction, of a source that emits monochromatic radiation of a frequency 540 x 1012 Hertz, and that has a radiant intensity in that direction of 1 / 683 watt per steradian.
SI base unit.		 LUMINANCE_INTENSITY 14 [I31-0, Table 1],
[I31-6, 6-29.a]
CD_PER_SQ_METRE cd/m2 luminance At a point on a surface and in a given direction, the luminous intensity of an element of the surface, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction. LUMINANCE 15 [I31-6, 6-32.a]
COULOMB C electric charge (quantity of electricity) The integral of electric current over time.
1 C = 1 s · A.		 ELECTRIC_CHARGE 16 [I31-0, Table 2],
[I31-5, 5-2.a]
electric flux Across a surface element, the scalar product of the electric flux density and the surface element. [I31-5, 5-8.a]
elementary charge The electric charge of a proton. [I31-8, 8-43.a],
[I31-9, 9-6.a]
COULOMB_METRE C · m electric dipole moment A vector quantity, the vector product of which with the electric field strength of a homogenous field is equal to the torque.
1 C · m = 1 m · s · A.		 ELECTRIC_DIPOLE-
_MOMENT		 17 [I31-5, 5-14.a]
electric dipole moment of a molecule A vector quantity, the vector product of which with the electric field strength is equal to the torque. [I31-8, 8-32.a]
COULOMB_METRE_SQD_PER_VOLT C · m2/V electric polarizability of a molecule The induced electric dipole moment divided by electric field strength.
1 C · m2/V = 1 (s4 · A2)/kg.		 ELECTRIC-
_POLARIZABILITY		 18 [I31-8, 8-33.a]
COULOMB_PER_CUBIC_M C/m3 volume charge (volume density of charge, electric charge density) The charge divided by volume.
1 C/m3 = 1 (s · A)/m3.		 VOLUME_DENSITY-
_CHARGE		 19 [I31-5, 5-3.a]
COULOMB_PER_KG C/kg exposure of ionizing radiation The total electric charge of the ions of the same sign produced when all the electrons (negative and positive) liberated by photons in an element of air are stopped in air, divided by the mass of that element.
1 C/kg = 1 (s · A)/kg.		 EXPOSURE 20 [I31-10, 10-58.a]
COULOMB_PER_KG_SEC C/(kg · s) exposure rate of ionizing radiation The exposure (ionizing radiation) divided by time.
1 C/(kg · s) = 1 A/kg.		 EXPOSURE_RATE 21 [I31-10, 10-59.a]
COULOMB_PER_MOLE C/mol molar charge The charge carried per amount of substance.
1 C/mol = 1 (s · A)/mol.		 MOLAR_CHARGE 22 [I31-8, 8-45.a]
COULOMB_PER_SQ_M C/m2 areic charge (surface density of charge) The charge divided by surface area.
1 C/m2 = 1 (s · A)/m2.		 SURFACE_DENSITY-
_CHARGE		 23 [I31-5, 5-4.a]
electric flux density A vector quantity, the divergence of which is equal to the volumic charge. [I31-5, 5-7.a]
electric polarization A vector quantity equal to the electric dipole moment per unit volume of a material. [I31-5, 5-13.a]
CUBIC_M_PER_CUBIC_M m3/m3 volume fraction (of B) The volume of B divided by the volume of the mixture.
1 m3/m3 = 1.		 VOLUME_FRACTION 24 [I31-8, 8-15.a],
[I31-0, 2.3.3]
CUBIC_METRE m3 section modulus The section modulus of a plane area (section) about an axis in its plane is the second moment of area divided by the distance from the axis to the most remote point of the area. VOLUME 25 [I31-3, 3-21.a]
volume The product of length, width and height. [I31-1, 1-6.a]
CUBIC_METRE_PER_COULOMB m3/C reciprocal volumic charge (reciprocal charge density) The volume divided by the charge. RECIPROCAL_VOLUMIC-
_CHARGE		 26 [I31-13, 13-20.a]
CUBIC_METRE_PER_KG m3/kg specific volume The volume divided by mass. SPECIFIC_VOLUME 27 [I31-3, 3-4.a]
CUBIC_METRE_PER_MOLE m3/mol molar volume The volume divided by the amount of substance. MOLAR_VOLUME 28 [I31-8, 8-6.a]
CUBIC_METRE_PER_SEC m3/s recombination coefficient The coefficient in the law of recombination. VOLUME_FLOW_RATE 29 [I31-10, 10-28.a]
volume flow rate The volume of matter which crosses a given surface, divided by time. [I31-3, 3-30.a],
[I31-7, 7-13.a]
DAY d time 1 d = 24 h = 86 400 s (exactly). TIME 31 [I31-0, Table 4],
[I31-1, 1-7.d]
DB dB field quantity ratio (level difference) A dimensionless quantity used to describe a comparison of field levels.
1 dB = 10-1 B (exactly) = 1,151 293 x 10-1Np (approximately).		 FIELD_OR_POWER-
_LEVEL_DIFF		 32 [I31-2, 2-9.a (remarks)]
power quantity ratio (level difference) A dimensionless quantity used to describe a comparison of power levels.
1 dB = 10-1 B (exactly) = 1,151 293 x 10-1Np (approximately).		 [I31-2, 2-10.a (remarks)],
[I1000, Annex A 7-21]
DB_PER_METRE dB/m power ratio (level difference) gradient The rate of power ratio change as a function of distance. POWER_LEVEL_DIFF-
_LEN_GRADIENT		 33 [I31-0, 2.3.2.2 (derived)]
DB_PER_METRE_KHZ dB/(m · kHz) power ratio (level difference) distance and frequency gradient The rate of power ratio change as a function of distance and spectral frequency. POWER_LEVEL_DIFF-
_LEN_FREQ		 34 [I31-0, 2.3.2.2 (derived)]
DB_PER_OCTAVE none power ratio (level difference) frequency gradient The rate of power ratio change as a function of spectral frequency octave. POWER_LEVEL_DIFF-
_FREQ_GRADIENT		 35 [I31-0, 2.3.2.2 (derived)]
DB_PER_SQ_METRE dB/m2 areic power ratio (level difference) The power level divided by area. AREIC_POWER_LEVEL-
_DIFF		 36 [I31-0, 2.3.2.2 (derived)]
DB_PER_SQ_METRE_KHZ dB/(m2 · kHz) gradient of power ratio (level difference) distance and frequency gradient The rate of change of power ratio change as a function of distance and spectral frequency. GRAD_POWER_LEVEL-
_DIFF_LEN_FREQ		 37 [I31-0, 2.3.2.2 (derived)]
DB_REF_ONE_MICROPASCAL dB (re 1 μPa) pressure power quantity ratio (level) 1 dB (re 1 μPa) is the level of a pressure power quantity when lg (P/P0) = 0,1 where P and P0 represent two pressure powers, P0 being a reference power of 1 μPa. PRESSURE_POWER_LEVEL 38 [I31-0, 2.3.2.2 (derived)]
DECAY_RATE %/min decay constant (disintegration constant) Probability of decay of an active species in a small time interval, divided by that interval.
1 %/min = 1 / 6 x 10-3 1/s (exactly).		 RATE 39 [I31-9, 9-36.a,
I31-0, 2.3.2.3]
DEGREE_ARC º Bragg angle The angle between an incident X-ray beam and a set of crystal planes for which the secondary radiation displays maximum intensity as a result of constructive interference. PLANE_ANGLE 40 [I31-13, 13-4.b]
plane angle The angle between two half-lines terminating at the same point is defined as the ratio of the length of the included arc of the circle (with its centre at that point) to the radius of that circle.
1º = (π / 180) rad (exactly).		 [I31-0, Table 4],
[I31-1, 1-1.b]
DEGREE_C ºC thermodynamic temperature A special name for the kelvin for use in stating values of Celsius temperature.
t = T - T0 where T0 = 273,15 K (exactly).		 THERMO_TEMPERATURE 41 [I31-0, Table 2],
[I31-4, 4-2.a]
DEGREE_C_PER_HOUR ºC/h thermodynamic temperature change rate The thermodynamic temperature change over an interval of time, divided by that time.
1 ºC/h = 1 / 3,6 x 10-3 K/s (exactly).		 THERMO_TEMP_CHANGE-
_RATE		 42 [I31-0, 2.3.2.2 and 2.3.4 (derived)]
DEGREE_C_PER_METRE ºC/m lineic thermodynamic temperature gradient The thermodynamic temperature change over a distance, divided by that distance.
1 ºC/m = 1 K/m (exactly).		 LINEIC_THERMO_TEMP-
_GRADIENT		 43 [I31-0, 2.3.2.2 (derived)]
DEGREE_C_PER_SEC ºC/s thermodynamic temperature change rate The thermodynamic temperature change over an interval of time, divided by that time.
1 ºC/s = 1 K/s (exactly).		 THERMO_TEMP_CHANGE-
_RATE		 44 [I31-0, 2.3.2.2 (derived)]
ELECTRONVOLT eV alpha disintegration energy The sum of the kinetic energy of the alpha particle produced in the disintegration process and the recoil energy of the product atom in the reference frame in which the emitting nucleus is at rest before its disintegration. ENERGY 45 [I31-9, 9-38.b]
average energy loss per ion pair formed (average energy loss per elementary charge of the same sign produced) The initial kinetic energy of an ionizing charged particle, divided by the total ionization produced by that particle. [I31-10, 10-25.b]
beta disintegration energy Sum of the maximum beta particle energy and the recoil energy of the atom produced in the reference frame in which the emitting nucleus is at rest before its disintegration. [I31-9, 9-40.b]
electron affinity The energy difference between an electron at rest at infinity and an electron at the lowest level of the conduction band in an insulator or semiconductor. [I31-13, 13-26.b]
energy The kinetic energy acquired by an electron in passing through a potential difference of 1 volt in a vacuum. Its value is experimentally determined as 1,602 177 x 10-19 J (approximately). [I31-0, Table 6],
[I31-9, 9-32.b]
exchange integral The interaction energy arising from electron exchange. [I31-13, 13-35.b]
Fermi energy In a metal, the highest energy of occupied states at zero thermodynamic temperature. [I31-13, 13-28.b]
gap energy Difference in energy between lowest level of conduction band and highest level of valence band. [I31-13, 13-28.b]
maximum beta particle energy Maximum energy of the energy spectrum in a beta disintegration process. [I31-9, 9-39.b]
reaction energy In a nuclear reaction, the sum of the kinetic and photon energies of the reaction products minus the sum of the kinetic and photon energies of the reactants. [I31-10, 10-1.b]
resonance energy Kinetic energy of an incident particle, in the reference frame of the target, corresponding to a resonance in a nuclear reaction. [I31-10, 10-2.b]
work function The energy difference between an electron at rest at infinity and an electron at the Fermi level in the interior of a substance. [I31-13, 13-25.b]
ELECTRONVOLT_M_SQD eV · m2 total atomic stopping power The total linear stopping power divided by the number density of the atoms in the substance.
1 eV · m2 = (1,602 177 33 ± 0,000 000 49) x 10-19 J · m2 (approximately).		 TOTAL_ATOMIC-
_STOPPING_POWER		 46 [I31-10, 10-19.b]
ELECTRONVOLT_M_SQD_PER_KG (eV · m2)/kg total mass stopping power The total linear stopping power divided by the volumic mass of the substance.
1 (eV · m2)/kg = (1,602 177 33 ± 0,000 000 49) x 10-19 (J · m2)/kg (approximately).		 TOTAL_MASS-
_STOPPING_POWER		 47 [I31-10, 10-20.b]
ELECTRONVOLT_PER_METRE eV/m linear energy transfer For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance. TOTAL_LINEAR-
_STOPPING_POWER		 48 [I31-10, 10-54.b]
total linear stopping power For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance; -dE/dx.
1 eV/m = (1,602 177 33 ± 0,000 000 49) x 10-19 J/m (approximately).		 [I31-10, 10-18.b]
FARAD F capacitance The charge divided by potential difference.
1 F = 1 C/V = 1 (s4 · A2)/(m2 · kg).		 CAPACITANCE 49 [I31-0, Table 2],
[I31-5, 5-9.a]
FARAD_PER_METRE F/m permittivity The ability of a material to resist the formation of an electric field within it.
1 F/m = 1 (s4 · A2)/(m3 · kg).		 PERMITTIVITY 50 [I31-5, 5-10.a]
GRAM g mass For historical reasons the name of the base unit for mass, the kg, contains the name of the SI prefix "kilo".
A gram is a special name given to unit kg x 10-3 that is used instead of "millikilogram".		 MASS 55 [I31-0, 3.2.4]
GRAM_PER_CUBIC_CM g/cm3 mass concentration (of B) The amount of substance of B divided by the volume of the mixture. VOLUMIC_MASS 56 [I31-8, 8-11.a]
volumic mass (mass density) The mass divided by the volume.
1 g/cm3 = 103 kg/m3 (exactly).		 [I31-3, 3-2.b],
[I31-0, 2.3.2.3],
[I31-7, 7-8.a]
GRAM_PER_CUBIC_M g/m3 mass concentration (of B) The amount of substance of B divided by the volume of the mixture. VOLUMIC_MASS 57 [I31-8, 8-11.a]
volumic mass (mass density) The mass divided by the volume.
1 g/m3 = 10-3 kg/m3 (exactly).		 [I31-3, 3-2.b],
[I31-0, 2.3.2.3],
[I31-7, 7-8.a]
GRAM_PER_GRAM g/g mass fraction (of B) The mass of B divided by the mass of the mixture.
1 g/g = 1 kg/kg = 1.		 MASS_FRACTION 58 [I31-8, 8-12.a],
[I31-0, 2.3.3],
[I31-0, 2.3.2.3]
GRAM_PER_KILOGRAM g/kg mass fraction (of B) The mass of B divided by the mass of the mixture.
1 g/kg = 10-3 kg/kg = 10-3 (exactly).		 MASS_FRACTION 59 [I31-8, 8-12.a],
[I31-0, 2.3.3],
[I31-0, 2.3.2.3]
GRAY Gy absorbed dose of ionizing radiation For any ionizing radiation, the energy imparted to an element of irradiated matter divided by the mass of this element.
1 Gy = 1 J/kg = 1 m2/s2.		 ABSORBED_DOSE 60 [I31-0, Table 3],
[I31-10, 10-51.a]
kerma For indirectly ionizing (uncharged) particles, the sum of the initial kinetic energies of all charged particles liberated in an element of matter, divided by the mass of that element. [I31-10, 10-55.a]
GRAY_PER_SECOND Gy/s absorbed dose rate of ionizing radiation The absorbed dose of ionizing radiation over an interval of time, divided by that time.
1 Gy/s = 1 W/kg = 1 m2/s3.		 ABSORBED_DOSE_RATE 61 [I31-10, 10-53.a]
kerma rate For indirectly ionizing (uncharged) particles, the sum of the initial kinetic energies of all charged particles liberated in an element of matter in a small interval of time, divided by the mass of that element and the interval of time. [I31-10, 10-56.a]
HENRY H magnetic inductance For a thin conducting loop, the magnetic flux through the loop, caused by an electric current in the loop, divided by that current.
For two thin conducting loops (m and n), the magnetic flux through one loop, due to an electric current in the other loop, divided by that current.
1 H = 1 Wb/A = 1 (m2 · kg)/(s2 · A2).		 INDUCTANCE 63 [I31-0, Table 2],
[I31-5, 5-22.a]
permeance The reciprocal of the reluctance of a magnetic circuit, determined by the magnetic flux divided by the magnetomotive force. [I31-5, 5-39.a]
HENRY_PER_METRE H/m magnetic permeability The ability of a substance to acquire magnetization when placed in a magnetic field.
1 H/m = 1 (m · kg)/(s2 · A2).		 MAGNETIC-
_PERMEABILITY		 64 [I31-5, 5-24.a]
HERTZ Hz frequency The number of cycles divided by time.
1 Hz = 1 s-1.		 FREQUENCY 65 [I31-0, Table 2],
[I31-2, 2-3.a],
[I31-6, 6-1.a],
[I31-7, 7-2.a]
rotational frequency The number of revolutions divided by time.
1 Hz = 1 s-1.		 [I31-5, 5-41.a]
HOUR h time 1 h = 60 min = 3 600 s (exactly). TIME 66 [I31-0, Table 4],
[I31-1, 1-7.c]
INT_SOLAR_FLUX_UNIT none international solar flux unit The unit of radio emission from the <SUN>, measured at a wavelength of 10.7 cm (approximately 2 800 MHz).
1 SFU = 104 Jy = 10-22 W/(m2 · Hz) (exactly).		 FLUX_DENSITY 67 [I31-0, 2.3.1 and 2.3.2 (derived)]
INV_CUBIC_CM 1/cm3 volumetric entity density (any elementary entity: atoms, molecules, ions, electrons, other particles, or specified groups of such particles) The number of molecules or particles divided by volume.
1/cm3 = 10-6 1/m3.		 VOLUMETRIC_ENTITY-
_DENSITY		 68 [I31-10, 10-27.a],
[I31-0, 2.3.2.3]
INV_CUBIC_CM_SEC 1/(cm3 · s) volumetric entity emittance or capture rate (any elementary entity: atoms, molecules, ions, electrons, other particles, or specified groups of such particles) The number of molecules or particles divided by volume, per time.
1/(cm3 · s) = 10-6 1/(m3 · s).		 VOLUMETRIC_ENTITY-
_EMIT_RATE		 69 [I31-10, 10-35.a],
[I31-0, 2.3.2.3]
INV_CUBIC_METRE 1/m3 electron number density (volumic electron number) The number density of electrons in conduction band. VOLUMETRIC_ENTITY-
_DENSITY		 70 [I31-13, 13-30.a]
ion number density (ion density) The number of positive or negative ions in a volume element, divided by that element. [I31-10, 10-27.a]
neutron number density The number of free neutrons in a volume element, divided by that element. [I31-10, 10-29.a]
volumetric entity density (any elementary entity: atoms, molecules, ions, electrons, other particles, or specified groups of such particles) The number of molecules or particles divided by their volume. [I31-8, 8-10.a]
INV_CUBIC_METRE_EV 1/(m3 · eV) density of states A function of the energy in a solid given by the number of permitted quantum states in the energy range between E and E + dE, per unit volume of the material.
1/(m3 · eV) = (6,241 5061 4 ± 0,0001 0011 9) x 1018 1/(m3 · J) (approximately).		 DENSITY_STATES 71 [I31-13, 13-17.b]
INV_CUBIC_METRE_JOULE 1/(m3 · J) density of states A function of the energy in a solid given by the number of permitted quantum states in the energy range between E and E + dE, per unit volume of the material. DENSITY_STATES 72 [I31-13, 13-17.a]
INV_CUBIC_METRE_SEC 1/(m3 · s) slowing-down density The number density of neutrons slowing down past a given energy value in a small time interval, divided by that interval. VOLUMETRIC_ENTITY-
_EMIT_RATE		 73 [I31-10, 10-35.a]
volumetric entity emittance or capture rate (any elementary entity: atoms, molecules, ions, electrons, other particles, or specified groups of such particles) The number of molecules or particles divided by volume, per time. [I31-10, 10-34.a]
INV_HENRY 1/H reluctance The magnetic potential difference divided by magnetic flux.
1/H = 1 A/Wb = 1 (s2 · A2)/(m2 · kg).		 RELUCTANCE 74 [I31-5, 5-38.a]
INV_KELVIN 1/K cubic expansion coefficient The coefficient of volumic expansion divided by the thermodynamic temperature change. LINEAR_EXPANSION-
_COEFF		 75 [I31-4, 4-3.a]
linear expansion coefficient The coefficient of linear expansion divided by the thermodynamic temperature change. [I31-4, 4-3.a]
relative pressure coefficient The coefficient of pressure change divided by the thermodynamic temperature change. [I31-4, 4-3.a]
INV_METRE 1/m angular reciprocal lattice vector A vector whose scalar products with all fundamental lattice vectors are integral multiples of 2π. INV_LENGTH 76 [I31-13, 13-2.a]
angular repetency (angular wave number) The reciprocal of the wavelength or the number of waves per unit angle along the direction of propagation. [I31-2, 2-7.b],
[I31-6, 6-5.b],
[I31-7, 7-7.b],
[I31-13, 13-10.b]
curvature The reciprocal of a radius of curvature. [I31-1, 1-4.a]
fundamental reciprocal lattice vectors The fundamental translation vectors for the reciprocal lattice. [I31-13, 13-2.a]
linear attenuation coefficient (linear extinction coefficient) The ratio of a quantity which is a function of distance divided by the distance between the measurements. [I31-6, 6-42.a],
[I31-10, 10-13.a]
linear ionization by a particle The number of elementary charges of the same sign produced over an element of length of the path of an ionizing charged particle, divided by that element. [I31-10, 10-23.a]
repetency (wavenumber) The reciprocal of the wavelength or the number of waves per unit length along the direction of propagation. [I31-2, 2-6.a],
[I31-6, 6-4.a],
[I31-7, 7-6.a]
vergence (lens power) The reciprocal of the distance between a point of reference and the point at which a pair of converging or diverging light rays intersect. [I31-6, 6-46.a]
volumic cross-section (macroscopic cross-section) Sum of the cross-sections for a reaction or process of a specified type over all atoms in a given volume, divided by that volume. [I31-10, 10-7.a]
INV_MICRON 1/μm angular repetency (angular wave number) The reciprocal of the wavelength or the number of waves per unit angle along the direction of propagation.
1 μm-1 = 106 1/m (exactly).		 INV_LENGTH 77 [I31-2, 2-7.b],
[I31-6, 6-5.b],
[I31-7, 7-7.b],
[I31-13, 13-10.b]
repetency (wavenumber) The reciprocal of the wavelength or the number of waves per unit length along the direction of propagation. [I31-2, 2-6.a],
[I31-6, 6-4.a],
[I31-7, 7-6.a]
INV_MOLE 1/mol molar density (Avogadro constant) The number of molecules divided by the amount of substance. MOLAR_DENSITY 78 [I31-8, 8-4.a]
INV_PASCAL 1/Pa bulk compressibility The reciprocal of the bulk modulus. COMPRESSIBILITY 79 [I31-3, 3-19.a]
compressibility The extent to which a material reduces its volume when it is subjected to compressive stresses.
1/Pa = 1 (m · s2)/kg.		 [I31-3, 3-19.a]
isentropic compressibility At a constant value of entropy, the extent to which a material reduces its volume when it is subjected to compressive stresses. [I31-4, 4-5.a]
isothermal compressibility At a constant temperature, the extent to which a material reduces its volume when it is subjected to compressive stresses. [I31-4, 4-5.a]
INV_RADIAN 1/rad reciprocal plane angle The reciprocal of the angle between two half-lines terminating at the same point is the ratio of the radius of a circle (with its centre at that point) to the length of the included arc of that circle.
1 rad-1 = 1 m/m = 1.		 RECIPROCAL_PLANE-
_ANGLE		 80 [I31-0, 2.3.2.2 (derived)]
INV_SEC_STERADIAN 1/(s · sr) photon intensity In a given direction from a source, the photon flux leaving the source, or an element of the source, in an element of solid angle containing the given direction, divided by that element of solid angle. PHOTON_INTENSITY 81 [I31-6, 6-24.a]
INV_SECOND 1/s angular frequency The frequency of rotation or vibration. RATE 82 [I31-2, 2-4.b],
[I31-5, 5-42.b],
[I31-7, 7-4.b]
angular frequency The number of cycles or revolutions divided by time. [I31-6, 6-2.b],
[I31-9, 9-14.b],
[I31-9, 9-15.b],
[I31-13, 13-11.b]
damping coefficient The factor defining the rate of exponential amplitude decay in a periodic or acoustic system. [I31-2, 2-11.a],
[I31-7, 7-23.a]
decay constant (disintegration constant) Probability of decay in a small time interval, divided by that interval. [I31-9, 9-36.a]
photon flux The number of photons in an incident beam of light received by a surface over a time interval. [I31-6, 6-23.a]
pulsatance The angular velocity of a periodic quantity. [I31-2, 2-4.b],
[I31-5, 5-42.b],
[I31-7, 7-4.b]
rotational frequency The number of revolutions divided by time. [I31-2, 2-3.b],
[I31-5, 5-41.b]
INV_SQ_CM_SEC_SR_EV 1/(cm2 · s · sr · eV) particle flux density within an energy range At a point on a surface and in a given direction, the charged particle flux of an element of the surface within an energy range of 1 eV centered on a given particle energy, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction, and divided by an element of solid angle containing the given direction.
1/(cm2 · s · sr · eV) = 10-6 1/(m2 · s · sr · eV) (exactly).		 PARTICLE_FLUX-
_DENSITY		 83 [I31-0, 2.3.2.3 (derived)]
INV_SQ_CM_SEC_SR_KEV 1/(cm2 · s · sr · KeV) particle flux density within an energy range At a point on a surface and in a given direction, the charged particle flux of an element of the surface within an energy range of 1 KeV centered on a given particle energy, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction, and divided by an element of solid angle containing the given direction.
1/(cm2 · s · sr · KeV) = 10-9 1/(m2 · s · sr · eV) (exactly, assuming an even distribution of particle energies).		 PARTICLE_FLUX-
_DENSITY		 84 [I31-0, 2.3.2.3 (derived)]
INV_SQ_CM_SEC_SR_MEV 1/(cm2 · s · sr · MeV) particle flux density within an energy range At a point on a surface and in a given direction, the charged particle flux of an element of the surface within an energy range of 1 MeV centered on a given particle energy, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction, and divided by an element of solid angle containing the given direction.
1/(cm2 · s · sr · MeV) = 10-12 1/(m2 · s · sr · eV) (exactly, assuming an even distribution of particle energies).		 PARTICLE_FLUX-
_DENSITY		 85 [I31-0, 2.3.2.3 (derived)]
INV_SQ_CM_SEC_STERADIAN 1/(cm2 · s · sr) photon luminance (photon radiance) At a point on a surface and in a given direction, the photon intensity of an element of the surface, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction.
1/(cm2 · s · sr) = 10-4 1/(m2 · s · sr) (exactly).		 PHOTON_LUMINANCE 86 [I31-6, 6-25.a],
[I31-0, 2.3.2.3]
INV_SQ_M_SEC_SR_EV 1/(m2 · s · sr · eV) particle flux density within an energy range At a point on a surface and in a given direction, the charged particle flux of an element of the surface within an energy range of 1 eV centered on a given particle energy, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction, and divided by an element of solid angle containing the given direction. PARTICLE_FLUX-
_DENSITY		 87 [I31-0, 2.3.2.2 (derived)]
INV_SQ_M_SEC_STERADIAN 1/(m2 · s · sr) photon luminance (photon radiance) At a point on a surface and in a given direction, the photon intensity of an element of the surface, divided by the area of the orthogonal projection of this element on a plane perpendicular to the given direction. PHOTON_LUMINANCE 88 [I31-6, 6-25.a]
INV_SQ_METRE 1/m2 areal entity density (any elementary entity: atoms, molecules, ions, electrons, other particles, or specified groups of such particles) At a given point in space, the number of particles incident on a small sphere, divided by the cross-sectional area of that sphere. AREAL_ENTITY_DENSITY 89 [I31-6, 6-28.a]
particle fluence At a given point in space, the number of particles incident on a small sphere, divided by the cross-sectional area of that sphere. [I31-10, 10-8.a]
INV_SQ_METRE_SEC 1/(m2 · s) current density of particles A vector quantity, the integral of whose normal component over any surface is equal to the net number of particles passing through that surface in a small time interval divided by that interval. PARTICLE_CURRENT-
_DENSITY		 90 [I31-10, 10-12.a]
particle fluence rate (particle flux density) At a given point in space, the number of particles incident on a small sphere in a small time interval, divided by the cross-sectional area of that sphere and by the time interval. [I31-10, 10-9.a],
[I31-10, 10-31.a]
photon exitance At a point on a surface, the photon flux leaving an element of the surface, divided by the area of that element and by the time interval. [I31-6, 6-26.a]
photon irradiance At a point on a surface, the photon flux incident on an element of the surface, divided by the area of that element and by the time interval. [I31-6, 6-27.a]
INV_STERADIAN 1/sr reciprocal solid angle The reciprocal of a solid angle of a cone is the ratio of the square of the radius of a sphere (with its centre at the apex of that cone) to the area cut out on a spherical surface.
1 sr-1 = 1 m2/m2 = 1.		 RECIPROCAL_SOLID-
_ANGLE		 91 [I31-0, 2.3.2.2 (derived)]
INV_STERADIAN_METRE 1/(sr · m) spectral reciprocal solid angle The reciprocal of a solid angle of a cone is the ratio of the square of the radius of a sphere (with its centre at the apex of that cone) to the area cut out on a spherical surface, as a function of radiant wavelength. SPECTRAL-
_RECIPROCAL_SOLID-
_ANGLE		 92 [I31-0, 2.3.2.2 (derived)]
INV_STERADIAN_MICRON 1/(sr · μm) spectral reciprocal solid angle The reciprocal of a solid angle of a cone is the ratio of the square of the radius of a sphere (with its centre at the apex of that cone) to the area cut out on a spherical surface, as a function of radiant wavelength.
1/(sr · μm) = 106 1/(sr · m) (exactly).		 SPECTRAL-
_RECIPROCAL_SOLID-
_ANGLE		 93 [I31-0, 2.3.2.2 (derived)]
JANSKY Jy flux density The amount of a given type of radiation that crosses a specified area within a specified period.
1 Jy = 10-26 W/(m2 · Hz) (exactly).		 FLUX_DENSITY 94 [I31-0, 2.3.1]
JOULE J alpha disintegration energy The sum of the kinetic energy of the alpha particle produced in the disintegration process and the recoil energy of the product atom in the reference frame in which the emitting nucleus is at rest before its disintegration. ENERGY 95 [I31-9, 9-38.a]
average energy loss per ion pair formed (average energy loss per elementary charge of the same sign produced) The initial kinetic energy of an ionizing charged particle, divided by the total ionization produced by that particle. [I31-10, 10-25.a]
beta disintegration energy Sum of the maximum beta particle energy and the recoil energy of the atom produced in the reference frame in which the emitting nucleus is at rest before its disintegration. [I31-9, 9-40.a]
electron affinity The energy difference between an electron at rest at infinity and an electron at the lowest level of the conduction band in an insulator or semiconductor. [I31-13, 13-26.a]
energy The amount of work.
1 J = 1 N·m = 1 (m2 · kg)/s2.		 [I31-0, Table 2],
[I31-3, 3-26.a]
energy imparted The energy imparted by ionizing radiation to the matter in a given volume is the difference between the sum of the energies of all the directly ionizing (charged) and indirectly ionizing (uncharged) particles which have entered the volume and the sum of the energies of all those which have left it, minus the energy equivalent of any increase in rest mass that has taken place in nuclear or elementary particle reactions within the volume. [I31-10, 10-50.a]
enthalpy Heat content. [I31-4, 4-20.a]
exchange integral The interaction energy arising from electron exchange. [I31-13, 13-35.a]
Fermi energy In a metal, the highest energy of occupied states at zero thermodynamic temperature. [I31-13, 13-28.a]
gap energy Difference in energy between lowest level of conduction band and highest level of valence band. [I31-13, 13-28.b]
heat (quantity of heat) Energy that is the result of the temperature difference between the boundary of a system and its surrounding environment. [I31-4, 4-6.a]
level width The uncertainty in energy (full width at half maximum) of an unstable state due to the finite lifetime of the state. [I31-9, 9-32.a]
maximum beta particle energy Maximum energy of the energy spectrum in a beta disintegration process. [I31-9, 9-39.a]
mean energy imparted The expectation value of the energy imparted. [I31-10, 10-50.a]
radiant energy The energy emitted, transferred or received as radiation. [I31-6, 6-7.a]
reaction energy In a nuclear reaction, the sum of the kinetic and photon energies of the reaction products minus the sum of the kinetic and photon energies of the reactants. [I31-10, 10-1.a]
resonance energy Kinetic energy of an incident particle, in the reference frame of the target, corresponding to a resonance in a nuclear reaction. [I31-10, 10-2.a]
work function The energy difference between an electron at rest at infinity and an electron at the Fermi level in the interior of a substance. [I31-13, 13-25.a]
JOULE_METRE_SQD J · m2 total atomic stopping power The total linear stopping power divided by the number density of the atoms in the substance.
1 J · m2 = 1 (m4 · kg)/s2.		 TOTAL_ATOMIC-
_STOPPING_POWER		 96 [I31-10, 10-19.a]
JOULE_METRE_SQD_PER_KG (J · m2)/kg total mass stopping power The total linear stopping power divided by the volumic mass of the substance.
1 (J · m2)/kg = 1 m4/s2.		 TOTAL_MASS-
_STOPPING_POWER		 97 [I31-10, 10-20.a]
JOULE_PER_CUBIC_M J/m3 radiant energy density The radiant energy in an element of volume, divided by that element. ENERGY_DENSITY 98 [I31-6, 6-8.a]
sound energy density (volumic sound energy) The mean sound energy in a given volume divided by that volume. [I31-7, 7-15.a]
volumic electromagnetic energy (electromagnetic energy density) The energy in an element of volume, divided by that element.
1 J/m3 = 1 kg/(m · s2).		 [I31-5, 5-30.a]
JOULE_PER_GRAM_K J/(g · K) massic entropy (specific entropy) The heat entropy divided by mass. SPECIFIC_HEAT-
_CAPACITY		 99 [I31-4, 4-19.a]
massic heat capacity (specific heat capacity) The heat capacity divided by mass.
1 J/(g · K) = 103 J/(kg · K) (exactly).		 [I31-4, 4-16.a],
[I31-0, 2.3.2.3]
JOULE_PER_KELVIN J/K Boltzmann constant A constant equal to 1,38 x 10-23 J/K, used in statistical physics. HEAT_CAPACITY 100 [I31-8, 8-37.a]
entropy When a small quantity of heat dQ is received by a system the thermodynamic temperature of which is T, the entropy of the system is increased by dQ/T, provided that no irreversible change takes place in the system. [I31-4, 4-18.a]
heat capacity The quantity dQ/dT, when the temperature of a system is increased by dT as a result of the addition of a small quantity of heat dQ.
1 J/K = 1 (m2 · kg)/(s2 · K).		 [I31-4, 4-15.a]
JOULE_PER_KELVIN_MOLE J/(K · mol) molar entropy The heat entropy divided by the amount of substance. MOLAR_ENTROPY 101 [I31-8, 8-9.a]
molar gas constant The universal constant of proportionality in the ideal gas law: pVm = RT. [I31-8, 8-36.a]
molar heat capacity The heat capacity divided by the amount of substance.
1 J/(K · mol) = 1 (m2 · kg)/(s2 · K · mol).		 [I31-8, 8-8.a]
JOULE_PER_KG J/kg specific energy The energy divided by mass.
1 J/kg = 1 m2/s2.		 SPECIFIC_ENERGY 102 [I31-4, 4-21.a]
JOULE_PER_KG_KELVIN J/(kg · K) massic entropy (specific entropy) The heat entropy divided by mass. SPECIFIC_HEAT-
_CAPACITY		 103 [I31-4, 4-19.a]
massic heat capacity (specific heat capacity) The heat capacity divided by mass.
1 J/(kg · K) = 1 m2/(s2 · K).		 [I31-4, 4-16.a]
JOULE_PER_KM J/km linear energy transfer For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance.
1 J/km = 10-3 J/m (exactly).		 LINEAR_ENERGY-
_TRANSFER		 104 [I31-10, 10-54.a]
total linear stopping power For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance; -dE/dx.
1 J/km = 1 x 10-3 J/m (exactly).		 [I31-10, 10-18.a,
I31-0, 2.3.2.3]
JOULE_PER_M_FOURTH_PWR J/m4 spectral concentration of radiant energy density (in terms of wavelength) The radiant energy density in an infinitesimal wavelength interval, divided by the range of that interval.
1 J/m4 = 1 kg/(m2 · s2).		 SPECTRAL_RAD-
_ENERGY_DENSITY		 105 [I31-6, 6-9.a]
JOULE_PER_METRE J/m linear energy transfer For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance.
1 J/m = 1 (m · kg)/s2.		 LINEAR_ENERGY-
_TRANSFER		 106 [I31-10, 10-54.a]
total linear stopping power For an ionizing charged particle, the energy imparted locally to matter in traversing a small distance through the matter, divided by that distance; -dE/dx. [I31-10, 10-18.a]
JOULE_PER_MOLE J/mol chemical potential A partial molar Gibbs free energy; the change in Gibbs free energy when one mole of a substance is added to a very large amount of a sample. MOLAR_ENERGY 107 [I31-8, 8-17.a]
molar thermodynamic energy The thermodynamic energy divided by the amount of substance.
1 J/mol = 1 (m2 · kg)/(s2 · mol).		 [I31-8, 8-7.a]
JOULE_PER_SQ_METRE J/m2 energy fluence At a given point in space, the sum of the energies, exclusive of rest energy, of all the particles incident on a small sphere, divided by the cross-sectional area of that sphere. RADIANT_ENERGY-
_FLUENCE		 108 [I31-10, 10-10.a]
radiant energy fluence At a given point in space, the radiant flux incident on a small sphere, divided by the cross-sectional area of that sphere.
1 J/m2 = 1 kg/s2.		 [I31-6, 6-11.a]
JOULE_SECOND J · s Planck constant 1 J · s = 1 (m2 · kg)/s. PLANCK_CONSTANT 109 [I31-9, 9-7.a]
KELVIN K thermodynamic temperature The fraction 1 / 273,16 of the thermodynamic temperature of the triple point of water.
SI base unit.		 THERMO_TEMPERATURE 110 [I31-0, Table 1],
[I31-4, 4-1.a],
[I31-13, 13-12.a],
[I31-13, 13-29.a],
[I31-13, 13-36.a]
KELVIN_PER_KM K/km lineic thermodynamic temperature gradient The thermodynamic temperature difference divided by distance.
1 K/km = 10-3 K/m (exactly).		 LINEIC_THERMO_TEMP-
_GRADIENT		 111 [I31-0, 2.3.2.2 (derived),
I31-0, 2.3.2.3]
KELVIN_PER_METRE K/m lineic thermodynamic temperature gradient The thermodynamic temperature difference divided by distance. LINEIC_THERMO_TEMP-
_GRADIENT		 112 [I31-0, 2.3.2.2 (derived)]
KELVIN_PER_SEC K/s thermodynamic temperature change rate The thermodynamic temperature change over an interval of time, divided by that time. THERMO_TEMP_CHANGE-
_RATE		 113 [I31-0, 2.3.2.2 and 2.3.4 (derived)]
KELVIN_PER_WATT K/W thermal resistance The temperature difference divided by heat flow rate.
1 K/W = 1 (m2 · kg · K)/s3.		 THERMAL_RESISTANCE 114 [I31-4, 4-12.a]
KG_METRE_PER_SEC kg · m/s momentum The product of mass and velocity. MOMENTUM 115 [I31-3, 3-8.a]
KG_METRE_SQD kg · m2 moment of inertia (about an axis) The sum (integral) of the products of the elements of mass of a body and the squares of their distances from an axis. MOMENT_INERTIA 116 [I31-3, 3-7.a]
KG_METRE_SQD_PER_SEC (kg · m2)/s moment of momentum (angular momentum) The moment of momentum of a particle about a point is equal to the vector product of the radius vector from this point to the particle and the momentum of the particle. ANGULAR_MOMENTUM 117 [I31-3, 3-11.a]
KG_PER_CUBIC_METRE kg/m3 mass concentration (of B) The amount of substance of B divided by the volume of the mixture. VOLUMIC_MASS 118 [I31-8, 8-11.a]
volumic mass (mass density) The mass divided by the volume. [I31-3, 3-2.a],
[I31-7, 7-8.a]
KG_PER_KG kg/kg mass fraction (of B) The mass of B divided by the mass of the mixture.
of the mixture.
1 kg/kg = 1.		 MASS_FRACTION 119 [I31-8, 8-12.a],
[I31-0, 2.3.3]
KG_PER_LITRE kg/l mass concentration (of B) The amount of substance of B divided by the volume of the mixture. VOLUMIC_MASS 120 [I31-8, 8-11.b]
volumic mass (mass density) The mass divided by the volume.
1 kg/l = 10-3 kg/m3 (exactly).		 [I31-3, 3-2.c]
KG_PER_METRE kg/m lineic mass (linear density) The mass divided by length. LINEIC_MASS 121 [I31-3, 3-5.a]
KG_PER_MOLE kg/mol molar mass The mass divided by the amount of substance. MOLAR_MASS 122 [I31-8, 8-5.a]
KG_PER_SECOND kg/s mass flow rate The mass of matter which crosses a given surface, divided by time. MASS_FLOW_RATE 123 [I31-3, 3-29.a]
KG_PER_SQ_METRE kg/m2 areic mass (surface density) The mass divided by area. SURFACE_DENSITY 124 [I31-3, 3-6.a]
mean mass range The mean linear range multiplied by the volumic mass of the substance. [I31-10, 10-22.a]
KILOGRAM kg mass The mass of the international prototype of the kilogram.
SI base unit.		 MASS 125 [I31-0, Table 1],
[I31-3, 3-1.a],
[I31-8, 8-31.a],
[I31-9, 9-4.a],
[I31-9, 9-5.a],
[I31-9, 9-28.a],
[I31-13, 13-31.a]
KM_PER_HOUR km/h velocity The distance divided by time.
1 km/h = 1 / 3,6 m/s (exactly).		 SPEED 127 [I31-1, 1-10.b]
LITRE l, L
(Both symbols are equally accepted.)		 volume The product of length, width and height.
1 l = 1 dm3 = 10-3 m3 (exactly).		 VOLUME 130 [I31-0, Table 4],
[I31-1, 1-6.b]
LITRE_PER_HOUR L/h volume flow rate The volume of matter which crosses a given surface, divided by time.
1 L/h = 1 / 3,6 x 10-6 m3/s (exactly).		 VOLUME_FLOW_RATE 131 [I31-0, 2.3.2.2 (derived)]
LITRE_PER_SECOND L/s volume flow rate The volume of matter which crosses a given surface, divided by time.
1 L/s = 10-3 m3/s (exactly).		 VOLUME_FLOW_RATE 132 [I31-0, 2.3.2.2 (derived)]
LUMEN lm luminous flux The rate of light emission.
1 lm = 1 cd · sr.		 LUMINANCE_FLUX 134 [I31-0, Table 2],
[I31-6, 6-30.a]
LUMEN_HOUR lm · h quantity of light The time integral of luminous flux.
1 lm · h = 3 600 lm · s (exactly).		 QUANTITY_LIGHT 135 [I31-6, 6-31.b]
LUMEN_PER_SQ_METRE lm/m2 luminous exitance At a point on a surface, the luminous flux leaving an element of the surface, divided by the area of that element. LUMINANCE_EXITANCE 136 [I31-6, 6-33.a]
LUMEN_PER_WATT lm/W luminous efficacy The luminous flux divided by power (radiant flux).
1 lm/W = 1 (s3 · lm)/(m2 · kg).		 LUMINANCE_EFFICIENCY 137 [I31-6, 6-36.a]
LUMEN_SECOND lm · s quantity of light The time integral of luminous flux. QUANTITY_LIGHT 138 [I31-6, 6-31.a]
LUX lx illuminance At a point on a surface, the luminous flux incident on an element of the surface, divided by the area of that element.
1 lx = 1 lm/m2.		 ILLUMINANCE 139 [I31-0, Table 2],
[I31-6, 6-34.a]
LUX_HOUR lx · h light exposure The time integral of illuminance.
1 lx · h = 3 600 lx · s (exactly).		 LIGHT_EXPOSURE 140 [I31-6, 6-35.b]
LUX_SECOND lx · s light exposure The time integral of illuminance. LIGHT_EXPOSURE 141 [I31-6, 6-35.a]