SIST EN 16981:2021
(Main)Photocatalysis - Glossary of terms
Photocatalysis - Glossary of terms
A common language for standards, disclosed to a wide audience and referring only to the operational protocols and to their outcomes, is needed both for a consistent set of standards and the connection with the scientific literature. This glossary will take into account existing glossary of terms used in photocatalysis and photochemistry. Because in photocatalysis numerous properties are difficult to be evaluated, it is strongly recommended in standard norms to avoid reporting properties depending on number of actives sites, the mechanisms of adsorption or kinetic mechanisms of photocatalytic reactions. For the same reason instead of the quantum yield and related quantities it is easier to report the photonic efficiency.
Most of the definitions reported in this document are a sub-set of the IUPAC definitions in photocatalysis and radiocatalysis [1]. Some other definitions, in particular for the photocatalytic rate and reactors are taken from a dedicated work [2]. The use and many technical specifications on the physical values suggested for irradiation conditions in the standards are reported in a separate Technical Specification [3].
The arrangement of entries is alphabetical, and the criterion adopted by the IUPAC has been followed for the typeface used: italicized words in a definition or following it indicate a cross-reference in the Glossary.
Photokatalyse - Glossar der Begriffe
Eine einheitliche Sprache wird für Normen, die für ein breites Publikum veröffentlicht werden und sich nur auf die Verfahrensprotokolle und deren Ergebnisse beziehen, sowohl für ein konsistentes Normenwerk als auch für die Verbindung zur wissenschaftlichen Literatur benötigt. Dieses Glossar wird bestehende Verzeichnisse von in der Photokatalyse und Photochemie verwendeten Begriffen berücksichtigen. Da in der Photokatalyse zahlreiche Eigenschaften zahlenmäßig schwer zu bestimmen sind, wird dringend empfohlen, in Standardanforderungen die Angabe von Eigenschaften, die von der Anzahl der aktiven Stellen, den Absorptionsmechanismen oder kinetischen Mechanismen der photokatalytischen Reaktionen abhängig sind, zu vermeiden. Aus dem gleichen Grund ist es leichter, statt der Quantenausbeute und verwandter Größen die photonische Leistung anzugeben.
Die meisten in diesem Dokument aufgeführten Definitionen sind eine Teilmenge der IUPAC-Definitionen in der Photokatalyse und Radiokatalyse [1]. Einige andere Definitionen, insbesondere für die photokatalytische Reaktionsgeschwindigkeit und Reaktoren, sind einer zugeordneten Veröffentlichung entnommen [2]. Die Anwendung und viele Technische Spezifikationen zu den physikalischen Werten, die für Einstrahlungs-bedingungen in den Normen vorgeschlagen wurden, sind in einer separaten Technischen Spezifikation wiedergegeben [3].
Die Einträge sind alphabetischN1 angeordnet und die von der IUPAC übernommenen Kriterien wurden für das Schriftbild befolgt: kursiv geschriebene Worte in oder nach einer Definition weisen auf einen Querverweis im Glossar hin.
N1 Nationale Fußnote: Die alphabetische Sortierung bezieht sich auf die englische Referenzfassung.
Photocatalyse - Glossaire de termes
Le glossaire donne une liste de définitions cohérentes utilisées dans les normes traitant de la photocatalyse à des fins de cohérence et de lien avec la littérature scientifique.
Fotokataliza - Slovar izrazov
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 16981:2021
01-december-2021
Nadomešča:
SIST-TS CEN/TS 16981:2017
Fotokataliza - Slovar izrazov
Photocatalysis - Glossary of terms
Photokatalyse - Glossar der Begriffe
Photocatalyse - Glossaire de termes
Ta slovenski standard je istoveten z: EN 16981:2021
ICS:
01.040.25 Izdelavna tehnika (Slovarji) Manufacturing engineering
(Vocabularies)
25.220.01 Površinska obdelava in Surface treatment and
prevleke na splošno coating in general
SIST EN 16981:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST EN 16981:2021
---------------------- Page: 2 ----------------------
SIST EN 16981:2021
EN 16981
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2021
EUROPÄISCHE NORM
ICS 01.040.25; 25.220.01 Supersedes CEN/TS 16981:2016
English Version
Photocatalysis - Glossary of terms
Photocatalyse - Glossaire de termes Photokatalyse - Glossar der Begriffe
This European Standard was approved by CEN on 18 July 2021.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16981:2021 E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
Contents Page
European foreword . 3
Introduction . 7
1 Scope . 8
2 Normative references and notes . 8
3 Terms and definitions . 8
Bibliography . 55
2
---------------------- Page: 4 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
European foreword
This document (EN 16981:2021) has been prepared by Technical Committee CEN/TC 386
“Photocatalysis”, under WG 1 “Terminology”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2022, and conflicting national standards shall be
withdrawn at the latest by April 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes CEN/TS 16981:2016.
In comparison with the previous edition, the following technical modifications have been made:
— Change of the Scope: “The glossary lists a consistent set of definitions to be used in standards on
photocatalysis for their consistency and connection with the scientific literature”.
— Change to Clause 2: Paragraphs were updated:
"Normative references and notes
There are no normative references in this document.
Most of the definitions reported in this document are a sub-set of the IUPAC definitions in
photocatalysis and radiocatalysis [1]. Some other definitions, in particular for the photocatalytic
rate and reactors, are taken from a dedicated work [2].
The technical specifications for the apparatus and physical values for irradiation conditions to be
used in the standards are reported in a separate Technical Specification [3].
For the magnitudes implying energy or photons incident on a surface from all directions, the set of
symbols recommended by the International Organization for Standardization (ISO) [4] and
included in the IUPAC “Green Book”, and by the International Commission on Illumination [5] are
adopted. This has been done primarily to comply with internationally agreed-upon symbols.”
— Clause 3: introductory wording and definitions were updated:
“ISO and IEC maintain a generic terminological databases for use in standardization, which could
complement this dedicated Glossary, at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
The arrangement of entries is alphabetical, and the criterion adopted by the IUPAC has been
followed for the typeface used: italicized words in a definition or following it indicate a cross-
reference in the Glossary.
SI units are adopted, with some exceptions, prominently in the use of the molar decadic absorption
coefficient, ε, with common units dm3 mol–1 cm–1 and a mole of photons denoted as an einstein.
As recently the definition of the SI units was established in terms of a set of seven defining
constants, including the Avogadro number, the mole (symbol: mol) is the base unit of amount
(number) of substance.
3
---------------------- Page: 5 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
Functional dependence of a physical quantity f on a variable x is indicated by placing the variable in
parentheses following the symbol for the function; e.g. ε(λ). Differentiation of a physical quantity f
with respect to a variable x is indicated by a subscript x; e.g. the typical spectral radiant power
quantity Pλ = dP/dλ. The natural logarithm is indicated with ln, and the logarithm to base 10 with
log.”
The following definitions were deleted:
— amalgam lamp (before 3.17),
— back electron-transfer (before 3.20)
— bioluminescence (before 3.25),
— charge-transfer (CT) absorption (before 3.35),
— charge-transfer (CT) complex (before 3.36),
— charge-transfer (CT) state (before 3.37),
— circular dichroism (CD) (before 3.43)
— charge hopping(before 3.31),
— circular dichroism (CD) (before 3.43),
— current yield see photocurrent yield(before 3.49),
— dielectric (before 3.59),
— differential quantum (before 3.60),
— diode light emitting (LED) (before 3.61),
— driving force (before 3.63),
— driving force (for electron transfer) (before 3.64),
— electron-transfer photosensitization (before 3.69),
— emissivity see emittance(before 3.73),
— excitation transfer see energy transfer (before 3.77),
— flash photolysis(before 3.85),
— FWHM(before 3.95),
— germicidal lamp(before 3.97),
— hypsochromic shift(before 3.103),
— inner-filter effect(before 3.106),
— inner-sphere electron transfer(before 3.107),
— interferometer(before 3.113),
— Lambert–Beer law (before 3.116),
— Lambert law (before 3.117),
— LED(before 3.119),
— light-emitting diode (LED) (before 3.121),
— low-pressure mercury lamp (arc) (before 3.123),
— medium-pressure mercury lamp (arc) (before 3.127),
— mercury–xenon lamp (arc) (before 3.129),
4
---------------------- Page: 6 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
— multiphoton process(before 3.132),
— OLED (before 3.135),
— OPA (before 3.137),
— OPO (before 3.138),
— optical multichannel analyzer (OMA) (before 3.140),
— optical parametric amplification process (before 3.141),
— optical parametric oscillator (OPO) (before 3.142),
— optoacoustic spectroscopy(before 3.143),
— photo-assisted catalysis(before 3.148),
— photohydration(before 3.166),
— photon emittance(before 3.174),
— photopolymerization(before 3.185),
— quartz–iodine lamp(before 3.194),
— radiant energy fluence rate(before 3.201),
— reactor CSTR(before 3.210),
— reflection factor (before 3.214),
— reflectivity(before 3.215),
— self-absorption (before 3.219),
— self-quenching (before 3.220),
— sensitizer (before 3.221),
— sensitization (before 3.222),
— singlet oxygen (before 3.223),
— singlet state(before 3.224),
— solvent shift(before 3.226),
— spectral radiant energy, Qλ(before 3.238),
— spectral sensitization(before 3.244),
— tungsten-halogen lamp(before 3.248),
— wolfram lamp(before 3.259),
The following definitions were updated:
— 3.11 actinic.
— 3.12 actinism.
— 3.18 attenuance filter
— 3.28 Brewster angle
— 3.64 extinction coefficient
— 3.65 Fermi level
— 3.71 fluorescence spectrum
5
---------------------- Page: 7 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
— 3.92 Fourier-transform spectrometer
— 3.93 Fourier-transform spectroscopy
— 3.95 mercury lamp
— 3.100 organic light-emitting device
— 3.102 phosphorescence
— 3.103 photoacoustic spectroscopy
— 3.113 photocuring
— 3.116 photodynamic effect
— 3.140 photoreaction
— 3.142 photosensitization
— 3.143 photosensitizer
— 3.145 quantum efficiency
— 3.152 radiant energy fluence
— 3.158 rate of photon absorption
— 3.159 reaction rate
— 3.160 reactor batch
— 3.163 red shift
— 3.165 RGB color model
— 3.191 UV dose
The following definitions were added:
— 3.137 photonic unit conversion
— 3.161 reactor continuous Stirred-Tank
— 3.162 reactor plug flow
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
6
---------------------- Page: 8 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
Introduction
Photocatalysis is a very efficient advanced oxidation technique which enables the production of active
species following light absorption by the photocatalyst, such as bound/free hydroxyl radicals (∙OH),
hydroperoxyl radicals (∙OOH) and other ROS, conduction band electrons and valence band holes,
capable of partly or completely mineralising/oxidising the majority of organic compounds. The most
commonly used photocatalyst is titanium dioxide (TiO ). Photocatalysts can be used in powder form or
2
deposited as thin films on different substrates (glass fibre, fabrics, plates/sheets, etc.). The objective of
standardization is to introduce test standards for evaluation of the performance of photocatalysts
(including photocatalysis and photo-induced effects). These standards mainly concern tests and
analysis methods, and require a common language.
A common language for standards, disclosed to a wide audience and referring only to the operational
protocols and to their outcomes, is needed for a consistent set of standards and the connection with the
scientific literature. This glossary will take into account existing glossary of terms and literature
definitions used in photocatalysis and photochemistry. Because in photocatalysis numerous properties
are difficult to be evaluated, in this Glossary and in related standard norms the report of properties
depending on some physical-chemical properties and model parameters, like the number of active sites,
the mechanisms of adsorption or kinetic mechanisms of photocatalytic reactions is avoided.
Safety statement
Persons using this document should be familiar with the normal laboratory practice, if applicable. This
document does not address safety problems, if any, associated with its use. It is the responsibility of the
user to establish appropriate safety and health practices and to ensure compliance with any regulatory
conditions.
Environmental statement
It is understood that some of the material described in this document may have negative environmental
impact. As technological advantages lead to better alternatives for these materials, they will be
eliminated from this document to the possible extent.
At the end of the test, the user of this document will take care to carry out an appropriate disposal of the
wastes, according to local regulation.
7
---------------------- Page: 9 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
1 Scope
The glossary lists a consistent set of definitions to be used in standards on photocatalysis for their
consistency and connection with the scientific literature.
2 Normative references and notes
There are no normative references in this document.
Most of the definitions reported in this document are a sub-set of the IUPAC definitions in
photocatalysis and radiocatalysis [1]. Some other definitions, in particular for the photocatalytic rate
and reactors, are taken from a dedicated work [2].
The technical specifications for the apparatus and physical values for irradiation conditions to be used
in the standards are reported in a separate Technical Specification [3].
For the magnitudes implying energy or photons incident on a surface from all directions, the set of
symbols recommended by the International Organization for Standardization (ISO) [4] and included in
the IUPAC “Green Book”, and by the International Commission on Illumination [5] are adopted. This has
been done primarily to comply with internationally agreed-upon symbols.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain a generic terminological databases for use in standardization, which could
complement this dedicated Glossary, at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
The arrangement of entries is alphabetical, and the criterion adopted by the IUPAC has been followed
for the typeface used: italicized words in a definition or following it indicate a cross-reference in the
Glossary.
SI units are adopted, with some exceptions, prominently in the use of the molar decadic absorption
3 –1 –1
coefficient, ε, with common units dm mol cm and a mole of photons denoted as an einstein. As
recently the definition of the SI units was established in terms of a set of seven defining constants,
including the Avogadro number, the mole (symbol: mol) is the base unit of amount (number) of
substance.
Functional dependence of a physical quantity f on a variable x is indicated by placing the variable in
parentheses following the symbol for the function; e.g. ε(λ). Differentiation of a physical quantity f with
respect to a variable x is indicated by a subscript x; e.g. the typical spectral radiant power
quantity P = dP/dλ. The natural logarithm is indicated with ln, and the logarithm to base 10 with log.
λ
8
---------------------- Page: 10 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.1
absorbance
A
logarithm to the base 10 (linear absorbance) of the incident (prior to absorption) spectral radiant power,
0
P divided by the transmitted spectral radiant power, P :
λ
λ
0
P
λ
ATλ = log =−log λ
( ) ( )
P
λ
Note 1 to entry: T(λ) is the (internal) transmittance at the defined wavelength. The terms absorbancy,
extinction, and optical density should not be used. When natural logarithms are used, the napierian absorbance is
0
the logarithm to the base e of the incident spectral radiant power, divided by the transmitted spectral radiant
P
λ
power, P :
λ
0
P
λ
A λ = ln =−lnT λ
( ) ( )
e
P
λ
Note 2 to entry: These definitions suppose that all the incident ultraviolet, visible, or infrared radiation is either
transmitted or absorbed, reflection or scattering being negligible. Attenuance should be used when this
supposition cannot be made.
Note 3 to entry: In practice, A is the logarithm to the base 10 of the spectral radiant power of ultraviolet, visible,
or infrared radiation transmitted through a reference sample divided by that transmitted through the investigated
sample, both observed in identical cells.
Note 4 to entry: In common usage, A is given for a path length of 1 cm, unless otherwise specified.
Note 5 to entry: Traditionally, (spectral) radiant intensity, I , was used instead of spectral radiant power, P ,
λ λ
now the accepted term.
Note 6 to entry: The wavelength symbol as a subscript for P and in parenthesis for T and A can be omitted.
However, the wavelength should be specified for which the value of the particular property is reported.
Note 7 to entry: Same as internal optical density, which is a term not recommended.
Note 8 to entry: See also absorption coefficient, absorptance, attenuance, Beer–Lambert law, molar absorption
coefficient.
3.2
absorbed spectral photon flux density
absorbed photon flux density
number of photons of a particular wavelength, per time interval (spectral photon flux, number basis,
q , or spectral photon flux, amount basis, q ) absorbed by a system per volume, V
p,λ n,p,λ
−1 –4 –1 –3 –1
Note 1 to entry: On number basis, SI unit is s m ; common unit is s cm nm . On amount basis, SI unit
–1 –4 −1 −3 –1
is mol s m ; common unit is einstein s cm nm .
− Aλ − Aλ
0 ( ) 0 ( )
q 1− 10 q 1− 10
p,λ n,p,λ
Note 2 to entry: Mathematical expression: on number basis, on
V V
amount basis, where A(λ) is the absorbance at wavelength λ and superscript 0 (zero) indicates incident photons.
9
---------------------- Page: 11 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
Note 3 to entry: Absorbed (spectral) photon flux density (number basis or amount basis) is used in the
denominator when calculating a differential quantum yield and using in the numerator the rate of change of the
number, dC/dt, or the rate of change of the amount concentration, dc/dt, respectively.
Note 4 to entry: The term rate of photon absorption is increasingly used.
3.3
absorbed spectral radiant power density
absorbed radiant power density
spectral radiant energy per time interval (spectral radiant power, P ) absorbed by a system per
λ
volume, V
–4 –3 –1
Note 1 to entry: SI unit is W m ; common unit is W cm nm .
− A(λ)
0
P 1-10
λ
Note 2 to entry: Mathematical expression: where A(λ) is the absorbance at wavelength λ and
V
superscript 0 (zero) indicates incident radiant power.
3.4
absorptance
a
fraction of ultraviolet, visible, or infrared radiation absorbed, equal to one minus the transmittance (T),
i.e., (1–T)
Note 1 to entry: The use of this obsolete term, equivalent to absorption factor, is not recommended.
Note 2 to entry: See also absorbance.
3.5
absorption
absorption of electromagnetic radiation
transfer of energy from an electromagnetic field to a material or a molecular entity
Note 1 to entry: In a semiclassical fashion, this transfer of energy can be described as being due to an
interaction of the electric field of the wave with an oscillating electric dipole moment set up in the material or
molecular entity. This dipole moment is the result of the perturbation by the outside field, and its oscillation
frequency ν is given by the difference ΔE of the energies of the lower and upper state in the absorbing material or
molecular entity, ΔE = hν. When the frequency of the oscillating dipole moment and the frequency of the field agree,
a resonance occurs and energy can flow from the field into the material or molecule (an absorption occurs).
Note 2 to entry: When energy flows from the material or molecule to the field, stimulated light emission occurs.
Note 3 to entry: The oscillating electric dipole moment produced in the material or molecular entity has an
amplitude and direction determined by a vector M , known as the electric transition (dipole) moment. The
if
amplitude of this moment is the transition moment between the initial (i) and final states (f).
10
---------------------- Page: 12 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.6
absorption coefficient
a(λ), α(λ)
absorbance, A(λ), divided by the optical pathlength, l:
0
A()λ 1 P
λ
a(λ ) log
ll P
λ
where a is the linear decadic absorption coefficient and
0
P
and P are, respectively, the incident and transmitted spectral radiant power.
λ
λ
When napierian logarithms are used
0
P
1
λ
αλ( ) a(λ )ln10 ln
lP
λ
where α is the linear napierian absorption coefficient.
–1
Note 1 to entry: Since absorbance is a dimensionless quantity, the coherent SI unit for a and α is m ; the
–1
common unit is cm .
Note 2 to entry: See also absorptivity, molar absorption coefficient.
3.7
absorption cross-section
σ
linear napierian absorption coefficient, α(λ), divided by the number of molecular entities contained in a
volume of the absorbing medium along the ultraviolet, visible, or infrared radiation path:
0
αλ
( ) 1 P
λ
σλ ln
( )
C C⋅l P
λ
where
C is the number concentration of molecular entities (number per volume), l is the optical pathlength,
0
P
and and P are, respectively, the incident and transmitted spectral radiant power.
λ
λ
2 2
Note 1 to entry: SI unit is m , common unit is cm .
Note 2 to entry: The relation between the absorption cross-section and the molar (decadic) absorption
coefficient, ε(λ), is α(λ) = ln10 ε(λ)/N with N the Avogadro constant. A conversion formula in common units is:
A A
2 −21 –1 3 –1
σ(λ)/cm = (3,8236 × 10 /mol) [ε(λ)/ mol dm cm ]
Note 3 to entry: See also attenuance, Beer–Lambert law.
11
==
==
==
---------------------- Page: 13 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.8
absorption factor
fraction of ultraviolet, visible, or infrared radiation absorbed by a system
–A(λ)
f(λ) = 1 – T(λ) = 1 – 10
with
T(λ) the transmittance and A(λ) the absorbance at a particular wavelength λ.
Note 1 to entry: This term is preferred to absorptance.
Note 2 to entry: The wavelength symbol can be omitted for f, T, and A. The wavelength should be specified for
which the value of the particular property is reported.
Note 3 to entry: For A(λ) << 1/ln10, f(λ) approximately A(λ) ln10.
3.9
absorption spectrum
plot of the absorption coefficient against a quantity related to photon energy, such as frequency ν,
wavenumber ν , or wavelength λ
Note 1 to entry: The plot of the absorbance against a quantity related to photon energy is discouraged, unless
the actual concentration of the species is unknown.
3.10
absorptivity
absorptance divided by the optical pathlength
Note 1 to entry: The unit length shall be specified.
Note 2 to entry: The use of this obsolete term is not recommended.
Note 3 to entry: For very low attenuance, i.e. for A(λ) << 1/ln10, it approximates the linear absorption
–A(λ)
coefficient, within the approximation [1 – 10 ] approximately A(λ) ln10.
3.11
actinic
chemical changes produced by radiant energy especially in the visible and ultraviolet parts of the
spectrum
Note 1 to entry: Applied to, resulting from, or referred to actinism.
3.12
actinism
chemical changes on living and nonliving materials caused by optical radiation especially in the visible
and ultraviolet parts of the spectrum
12
---------------------- Page: 14 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.13
actinometer
chemical system for the determination of the number of photons integrally or per time interval
absorbed into the defined space of a chemical reactor
Note 1 to entry: This name is commonly applied to systems used in the ultraviolet and visible wavelength
ranges.
Note 2 to entry: For example, solutions of potassium oxalatoferrate(III), K [Fe(C O ) ] (among other systems)
3 2 4 3
can be used as a chemical actinometer. Bolometers, thermopiles, and photodiodes are physical devices giving a
reading of the radiation impinging on them that can be correlated to the number of photons detected as well as to
the number of photons entering the chemical reactor. Detailed information on chemical actinometers and
measuring systems can be found in CEN/TS 16599:2014.
Note 3 to entry: See also spectral sensitivity.
3.14
action spectrum
plot of a relative biological or chemical photoresponse (=Δy) per number of incident (prior to
absorption) photons, vs. wavelength, or energy of radiation, or frequency or wavenumber
Note 1 to entry: This form of presentation is frequently used in the studies of biological or solid-state systems,
where the nature of the absorbing species is unknown.
Note 2 to entry: It is advisable to ensure that the fluence dependence of the photoresponse is the same
(e.g. linear) for all the wavelengths studied.
Note 3 to entry: The action spectrum is sometimes called spectral responsivity or sensitivity spectrum. The
precise action spectrum is a plot of the spectral (photon or quantum) effectiveness. By contrast, a plot of the
biological or chemical change or response per absorbed photon (quantum efficiency) vs. wavelength is the
efficiency spectrum.
Note 4 to entry: In cases where the fluence dependence of the photoresponse is not linear (as is often the case in
biological photoresponses), a plot of the photoresponse vs. fluence should be made at several wavelengths and a
standard response should be chosen. A plot of the inverse of the “standard response” level vs. wavelength is then
the action spectrum of the photoresponse.
Note 5 to entry: See also excitation spectrum, efficiency spectrum.
3.15
AM 0 sunlight
solar irradiance in space just above the atmosphere of the earth on a plane perpendicular to the
direction of the sun (air mass, AM, zero)
Note 1 to entry: Also called extraterrestrial irradiance.
Note 2 to entry: See also AM 1 sunlight.
3.16
AM 1 sunlight
solar irradiance at sea level, i.e., traversing the atmosphere, when the direction of the sun is
perpendicular to the surface of the earth
Note 1 to entry: Also called terrestrial global irradiance.
Note 2 to entry: See also AM 0 sunlight.
13
---------------------- Page: 15 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.17
attenuance
D
0
logarithm to the base 10 of the incident spectral radiant power, P , divided by the transmitted spectral
λ
radiant power, P
λ
0
P
λ
D(λλ)= log =−logT
( )
P
λ
where
T(λ) is the transmittance.
Note 1 to entry: Attenuance reduces to absorbance if the incident beam is only either transmitted or absorbed,
but not reflected or scattered.
Note 2 to entry: See also Beer–Lambert law, depth of penetration.
3.18
attenuance filter
neutral-density filter
filter that reduces or modifies the transmitted radiant power of all wavelengths of light equally, giving
no changes in hue of color rendition
Note 1 to entry: The term neutral-density filter is preferred.
Note 2 to entry: Detailed information on filters can be found in CEN/TS 16599:2014.
3.19
bandgap energy
E
g
energy difference between the bottom of the conduction band and the top of the valence band in a
semiconductor or an insulator
Note 1 to entry: See also Fermi level, conduction band, valence band.
3.20
bandpass filter
optical device that permits the transmission of radiation within a specified wavelength range and does
not permit transmission of radiation at higher or lower wavelengths
Note 1 to entry: It can be an interference or a coloured filter.
Note 2 to entry: See also filter. More detailed info on filters can be found in CEN/TS 16599:2014.
3.21
bathochromic shift
shift of a spectral band to lower frequency (longer wavelengths) owing to the influence of substitution or
a change in environment (e.g., solvent)
Note 1 to entry: It is informally referred to as a red shift and is opposite to a hypsochromic shift.
14
---------------------- Page: 16 ----------------------
SIST EN 16981:2021
EN 16981:2021 (E)
3.22
Beer–Lambert law
Lambert-Beer law
Beer–Lambert–Bouguer law
relation of the absorbance of a beam of collimated monochromatic radiation in a homogeneous isotropic
medium with the absorption pathlength, l, and the concentration, c, or (in the gas phase) the pressure of
the absorbing species
Note 1 to entry: This law holds only under the limitations above, for low light radiant power and for absorbing
species exhibiting no concentration or pressure dependent aggregation. The law can be expressed as
0
P
λ
A(λ)
...
SLOVENSKI STANDARD
oSIST prEN 16981:2020
01-junij-2020
Fotokataliza - Slovar izrazov
Photocatalysis - Glossary of terms
Photokatalyse - Glossar der Begriffe
Photocatalyse - Glossaire de termes
Ta slovenski standard je istoveten z: prEN 16981
ICS:
01.040.25 Izdelavna tehnika (Slovarji) Manufacturing engineering
(Vocabularies)
25.220.01 Površinska obdelava in Surface treatment and
prevleke na splošno coating in general
oSIST prEN 16981:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN 16981:2020
---------------------- Page: 2 ----------------------
oSIST prEN 16981:2020
DRAFT
EUROPEAN STANDARD
prEN 16981
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2020
ICS 01.040.25; 25.220.01 Will supersede CEN/TS 16981:2016
English Version
Photocatalysis - Glossary of terms
Photocatalyse - Glossaire de termes Photokatalyse - Glossar der Begriffe
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 386.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 16981:2020 E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Generalities . 5
2.1 Note on units . 5
2.2 Note on symbols . 5
2.3 Note on the relationship between spectral, radiometric, and photonic quantities . 5
3 Terms and definitions . 6
Bibliography . 47
2
---------------------- Page: 4 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
European foreword
This document (prEN 16981:2020) has been prepared by Technical Committee CEN/TC 386
“Photocatalysis”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
3
---------------------- Page: 5 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
Introduction
Photocatalysis is a very efficient advanced oxidation technique which enables the production of active
species following light absorption by the photocatalyst, such as bound/free hydroxyl radicals (∙OH),
hydroperoxyl radicals (∙OOH), conduction band electrons and valence band holes, capable of partly or
completely mineralising/oxidising the majority of organic compounds. The most commonly used
photocatalyst is titanium dioxide (TiO ), because it is thermodynamically stable, non-toxic and
2
economical. Photocatalysts can be used in powder form or deposited as thin film on different substrates
(glass fibre, fabrics, plates/sheets, etc.). The objective of standardization is to introduce test standards
for evaluation of the performance of photocatalysts (including photocatalysis and photo-induced effects).
These standards mainly concern tests and analysis methods, and require a common language.
Safety statement
Persons using this document should be familiar with the normal laboratory practice, if applicable. This
document does not address safety problems, if any, associated with its use. It is the responsibility of the
user to establish appropriate safety and health practices and to ensure compliance with any regulatory
conditions.
Environmental statement
It is understood that some of the material described in this document may have negative environmental
impact. As technological advantages lead to better alternatives for these materials, they will be eliminated
from this document to the possible extent.
At the end of the test, the user of this document will take care to carry out an appropriate disposal of the
wastes, according to local regulation.
4
---------------------- Page: 6 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
1 Scope
A common language for standards, disclosed to a wide audience and referring only to the operational
protocols and to their outcomes, is needed both for a consistent set of standards and the connection with
the scientific literature. This glossary will take into account existing glossary of terms used in
photocatalysis and photochemistry. Because in photocatalysis numerous properties are difficult to be
evaluated, it is strongly recommended in standard norms to avoid reporting properties depending on
number of actives sites, the mechanisms of adsorption or kinetic mechanisms of photocatalytic reactions.
For the same reason instead of the quantum yield and related quantities it is easier to report the photonic
efficiency.
Most of the definitions reported in this document are a sub-set of the IUPAC definitions in photocatalysis
and radiocatalysis [1]. Some other definitions, in particular for the photocatalytic rate and reactors are
taken from a dedicated work [2]. The use and many technical specifications on the physical values
suggested for irradiation conditions in the standards are reported in a separate Technical Specification
[3].
The arrangement of entries is alphabetical, and the criterion adopted by the IUPAC has been followed for
the typeface used: italicized words in a definition or following it indicate a cross-reference in the Glossary.
2 Generalities
2.1 Note on units
SI units are adopted, with some exceptions, prominently in the use of the molar decadic absorption
3 –1 –1
coefficient, ε, with common units dm mol cm and a mole of photons denoted as an einstein. As recently
the definition of the SI units was established in terms of a set of seven defining constants, including the
Avogadro number, the mole (symbol: mol) is the base unit of amount (number) of substance.
2.2 Note on symbols
Functional dependence of a physical quantity f on a variable x is indicated by placing the variable in
parentheses following the symbol for the function; e.g. ε(λ). Differentiation of a physical quantity f with
respect to a variable x is indicated by a subscript x; e.g. the typical spectral radiant power quantity P =
λ
dP/dλ. The natural logarithm is indicated with ln, and the logarithm to base 10 with log.
For the magnitudes implying energy or photons incident on a surface from all directions, the set of
symbols recommended by the International Organization for Standardization (ISO) [4] and included in
the IUPAC “Green Book”, and by the International Commission on Illumination [5] are adopted, i.e. H or
o
F for fluence, E for fluence rate, H or F for photon fluence, and E for photon fluence rate, note the
o o p,o p,o p,o
letter o as subscript. This has been done primarily to comply with internationally agreed-upon symbols.
It is important, however, to avoid confusion with the terms used to designate an amount of energy (or
photons) prior to absorption. In these cases, the superscript 0 (zero) is used.
2.3 Note on the relationship between spectral, radiometric, and photonic quantities
When a quantity expressed in photonic units (G ) covers a wavelength range (polychromatic irradiation
p
between λ and λ ), then G is the integral between λ and λ of the corresponding spectral photonic
1 2 p 1 2
quantity, G (λ):
p
λ 2
G = G (λ) dλ (e.g., spectral photon flux)
p p
∫
λ1
5
---------------------- Page: 7 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
Since a spectral radiometric or energetic quantity at a given wavelength λ (G , e.g. spectral radiant power,
e,λ
−1
P nm , is related to the corresponding photonic quantity at the same wavelength (G , e.g. spectral
λ/W p,λ
−1 −1
photon flux / s nm ) by the relation:
G = E(λ) G
e,λ p,λ
with
E(λ) = h c/λ, the energy of a photon of wavelength λ.
The relation between photonic (G ) and corresponding radiometric (or energetic, G ) quantity is given
p e
by:
λ 2
G = h c G (λ) 1/λ dλ
e p
∫
λ1
or, more useful in practice:
λ 2
G = (1/h c) G (λ)λ dλ
p e
∫
λ1
Therefore, for example, to calculate a photon flux over a wavelength interval, the spectral distribution of
the radiant power is necessary. Note that in the Glossary no sub-index e has been used for the radiometric
quantities. Radiometric quantities (G , as above, radiant power and others) are needed because lamp
e
providers usually give the spectral distribution of the lamps in these units, and not in photonic units (G ,
p
photon flux and other photonic quantities) and because of quantification of radiation using, e.g.
radiometers.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
absorbance, Ae
logarithm to the base 10 (linear absorbance) of the incident (prior to absorption) spectral radiant power,
0
P divided by the transmitted spectral radiant power, P :
λ
λ
0
P
λ
A λλ= log =−logT
( ) ( )
P
λ
Note 1 to entry: T(λ) is the (internal) transmittance at the defined wavelength. The terms absorbancy, extinction,
and optical density should not be used. When natural logarithms are used, the napierian absorbance is the logarithm
0
P divided by the transmitted spectral radiant power, P :
to the base e of the incident spectral radiant power, λ
λ
0
P
λ
A λλ= ln =−lnT
( ) ( )
e
P
λ
Note 2 to entry: These definitions suppose that all the incident ultraviolet, visible, or infrared radiation is either
transmitted or absorbed, reflection or scattering being negligible. Attenuance should be used when this supposition
cannot be made.
6
---------------------- Page: 8 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
Note 3 to entry: In practice, A is the logarithm to the base 10 of the spectral radiant power of ultraviolet, visible,
or infrared radiation transmitted through a reference sample divided by that transmitted through the investigated
sample, both observed in identical cells.
Note 4 to entry: In common usage, A is given for a path length of 1 cm, unless otherwise specified.
Note 5 to entry: Traditionally, (spectral) radiant intensity, I , was used instead of spectral radiant power, P , now
λ λ
the accepted term.
Note 6 to entry: The wavelength symbol as a subscript for P and in parenthesis for T and A may be omitted.
However, the wavelength should be specified for which the value of the particular property is reported.
Note 7 to entry: Same as internal optical density, which is a term not recommended.
Note 8 to entry: See also absorption coefficient, absorptance, attenuance, Beer–Lambert law, Lambert law, molar
absorption coefficient.
3.2
absorbed (spectral) photon flux density
number of photons of a particular wavelength, per time interval (spectral photon flux, number basis, q ,
p,λ
or spectral photon flux, amount basis, q ) absorbed by a system per volume, V
n,p,λ
−1 –4 –1 –3 –1
Note 1 to entry: On number basis, SI unit is s m ; common unit is s cm nm . On amount basis, SI unit is mol
–1 –4 −1 −3 –1
m ; common unit is einstein s cm nm .
s
− Aλ − Aλ
( ) ( )
0 0
q 1− 10 q 1− 10
p,λ n,p,λ
Note 2 to entry: Mathematical expression: on number basis, on amount
V V
basis, where A(λ) is the absorbance at wavelength λ and superscript 0 (zero) indicates incident photons.
Note 3 to entry: Absorbed (spectral) photon flux density (number basis or amount basis) is used in the
denominator when calculating a differential quantum yield and using in the numerator the rate of change of the
number, dC/dt, or the rate of change of the amount concentration, dc/dt, respectively.
3.3
absorbed (spectral) radiant power density
spectral radiant energy per time interval (spectral radiant power, P ) absorbed by a system per volume, V
λ
–4 –3 –1
Note 1 to entry: SI unit is W m ; common unit is W cm nm .
− Aλ
( )
0
P 1-10
λ
Note 2 to entry: Mathematical expression: where A(λ) is the absorbance at wavelength λ and
V
superscript 0 (zero) indicates incident radiant power.
3.4
absorptance, a
fraction of ultraviolet, visible, or infrared radiation absorbed, equal to one minus the transmittance (T),
i.e., (1 - T)
Note 1 to entry: The use of this obsolete term, equivalent to absorption factor, is not recommended.
Note 2 to entry: See also absorbance.
7
---------------------- Page: 9 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
3.5
absorption (of electromagnetic radiation)
transfer of energy from an electromagnetic field to a material or a molecular entity
Note 1 to entry: In a semiclassical fashion, this transfer of energy can be described as being due to an interaction
of the electric field of the wave with an oscillating electric dipole moment set up in the material or molecular entity.
This dipole moment is the result of the perturbation by the outside field, and its oscillation frequency ν is given by
the difference ΔE of the energies of the lower and upper state in the absorbing material or molecular entity, ΔE = hν.
When the frequency of the oscillating dipole moment and the frequency of the field agree, a resonance occurs and
energy can flow from the field into the material or molecule (an absorption occurs).
Note 2 to entry: When energy flows from the material or molecule to the field, stimulated light emission occurs.
Note 3 to entry: The oscillating electric dipole moment produced in the material or molecular entity has an
amplitude and direction determined by a vector Mif, known as the electric transition (dipole) moment. The
amplitude of this moment is the transition moment between the initial (i) and final states (f).
3.6
absorption coefficient (linear decadic a or linear napierian α)
absorbance, A(λ), divided by the optical pathlength, l:
0
P
A()λ
1
λ
a(λ) log
ll P
λ
where
0
P and P are, respectively, the incident and transmitted spectral radiant power. When napierian
λ
λ
logarithms are used
0
P
1
λ
αλ( ) a(λ)ln 10 ln
lP
λ
where
α is the linear napierian absorption coefficient
–1
Note 1 to entry: Since absorbance is a dimensionless quantity, the coherent SI unit for a and α is m ; the common
–1
unit is cm .
Note 2 to entry: See also absorptivity, molar absorption coefficient.
3.7
absorption cross-section, σ
linear napierian absorption coefficient, α(λ), divided by the number of molecular entities contained in a
volume of the absorbing medium along the ultraviolet, visible, or infrared radiation path:
0
P
a()λ
1
λ
σλ( ) ln
C Cl P
λ
where
8
==
==
==
---------------------- Page: 10 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
C is the number concentration of molecular entities (number per volume), l is the optical pathlength,
0
and P and P are, respectively, the incident and transmitted spectral radiant power
λ
λ
2 2
Note 1 to entry: SI unit is m , common unit is cm .
Note 2 to entry: The relation between the absorption cross-section and the molar (decadic) absorption coefficient,
ε(λ), is α(λ) = ln10 ε(λ)/NA with NA the Avogadro constant. A conversion equation in common units is:
2 −21 –1 3 –1
σ(λ)/cm = (3.8236 × 10 /mol) × [ε(λ)/ mol dm cm ]
Note 3 to entry: See also attenuance, Beer–Lambert law.
3.8
absorption factor
fraction of ultraviolet, visible, or infrared radiation absorbed by a system
–A(λ)
f(λ) = 1 – T(λ) = 1 – 10
with
T(λ) the transmittance and A(λ) the absorbance at a particular wavelength λ
Note 1 to entry: This term is preferred to absorptance.
Note 2 to entry: The wavelength symbol may be omitted for f, T, and A. The wavelength should be specified for
which the value of the particular property is reported.
Note 3 to entry: For A(λ) << 1/ln10, f(λ) approximately A(λ) ln10.
3.9
absorption spectrum
plot of the absorbance or of the absorption coefficient against a quantity related to photon energy, such as
frequency ν, wavenumber ν , or wavelength λ
3.10
absorptivity
absorptance divided by the optical pathlength
Note 1 to entry: The unit length shall be specified.
Note 2 to entry: The use of this obsolete term is not recommended.
Note 3 to entry: For very low attenuance, i.e. for A(λ) << 1/ln10, it approximates the linear absorption coefficient,
–A(λ)
within the approximation [1 – 10 ] approximately A(λ) ln10.
3.11
actinic
applied or referred to actinism. Relating to, resulting from, or exhibiting chemical changes produced by
radiant energy especially in the visible and ultraviolet parts of the spectrum
3.12
actinism
chemical changes on living and nonliving materials caused by optical radiation
9
---------------------- Page: 11 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
3.13
actinometer
chemical system for the determination of the number of photons integrally or per time interval absorbed
into the defined space of a chemical reactor
Note 1 to entry: This name is commonly applied to systems used in the ultraviolet and visible wavelength ranges.
Note 2 to entry: For example, solutions of potassium oxalatoferrate(III), K3[Fe(C2O4)3] (among other systems)
can be used as a chemical actinometer. Bolometers, thermopiles, and photodiodes are physical devices giving a
reading of the radiation impinging on them that can be correlated to the number of photons detected as well as to
the number of photons entering the chemical reactor. Detailed information on chemical actinometers and
measuring systems can be found in CEN/TS 16599:2014.
Note 3 to entry: See also spectral sensitivity.
3.14
action spectrum
plot of a relative biological or chemical photoresponse (=Δy) per number of incident (prior to absorption)
photons, vs. wavelength, or energy of radiation, or frequency or wavenumber
Note 1 to entry: This form of presentation is frequently used in the studies of biological or solid-state systems,
where the nature of the absorbing species is unknown.
Note 2 to entry: It is advisable to ensure that the fluence dependence of the photoresponse is the same (e.g. linear)
for all the wavelengths studied.
Note 3 to entry: The action spectrum is sometimes called spectral responsivity or sensitivity spectrum. The precise
action spectrum is a plot of the spectral (photon or quantum) effectiveness. By contrast, a plot of the biological or
chemical change or response per absorbed photon (quantum efficiency) vs. wavelength is the efficiency spectrum.
Note 4 to entry: In cases where the fluence dependence of the photoresponse is not linear (as is often the case in
biological photoresponses), a plot of the photoresponse vs. fluence should be made at several wavelengths and a
standard response should be chosen. A plot of the inverse of the “standard response” level vs. wavelength is then
the action spectrum of the photoresponse.
Note 5 to entry: See also excitation spectrum, efficiency spectrum.
3.15
AM 0 sunlight
solar irradiance in space just above the atmosphere of the earth on a plane perpendicular to the direction
of the sun (air mass, AM, zero)
Note 1 to entry: Also called extraterrestrial irradiance.
Note 2 to entry: See also AM 1 sunlight.
3.16
AM 1 sunlight
solar irradiance at sea level, i.e., traversing the atmosphere, when the direction of the sun is perpendicular
to the surface of the earth
Note 1 to entry: Also called terrestrial global irradiance.
Note 2 to entry: See also AM 0 sunlight.
10
---------------------- Page: 12 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
3.17
attenuance, D
0
logarithm to the base 10 of the incident spectral radiant power, P , divided by the transmitted spectral
λ
radiant power, P
λ
0
P
λ
DT(λλ)= log =−log
( )
P
λ
where
T(λ) is the transmittance
Note 1 to entry: Attenuance reduces to absorbance if the incident beam is only either transmitted or absorbed,
but not reflected or scattered.
Note 2 to entry: See also Beer–Lambert law, depth of penetration.
3.18
attenuance filter
(better use: neutral-density filter)
Note 1 to entry: Detailed information on filters can be found in CEN/TS 16599:2014
3.19
back electron-transfer
term often used to indicate thermal inversion of excited-state electron transfer restoring the donor and
acceptor in their original oxidation state
Note 1 to entry: Process better designated as electron back-transfer.
Note 2 to entry: In using this term, one should also specify the resulting electronic state of the donor and acceptor.
Note 3 to entry: It is recommended to use this term only for the process restoring the original electronic state of
donor and acceptor.
Note 4 to entry: Should the forward electron transfer lead to charge separation, electron back-transfer will result
in charge recombination.
3.20
bandgap energy, E
g
energy difference between the bottom of the conduction band and the top of the valence band in a
semiconductor or an insulator
Note 1 to entry: See also Fermi level.
3.21
bandpass filter
optical device that permits the transmission of radiation within a specified wavelength range and does
not permit transmission of radiation at higher or lower wavelengths
Note 1 to entry: It can be an interference or a coloured filter.
Note 2 to entry: See also filter. More detailed info on filters can be found in CEN/TS 16599:2014.
11
---------------------- Page: 13 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
3.22
bathochromic shift (effect)
shift of a spectral band to lower frequency (longer wavelengths) owing to the influence of substitution or
a change in environment (e.g., solvent)
Note 1 to entry: It is informally referred to as a red shift and is opposite to a hypsochromic shift.
3.23
Beer–Lambert law (or Beer–Lambert–Bouguer law)
the absorbance of a beam of collimated monochromatic radiation in a homogeneous isotropic medium is
proportional to the absorption pathlength, l, and to the concentration, c, or (in the gas phase) to the
pressure of the absorbing species
Note 1 to entry: This law holds only under the limitations of the Lambert law and for absorbing species exhibiting
no concentration or pressure dependent aggregation. The law can be expressed as
0
P
λ
A(λ) log ελ cl
( )
P
λ
or
−−Aλ ε λ cl
( ) ( )
00
PP 10 P 10
λλ λ
0
where the proportionality constant, ε(λ), is the molar (decadic) absorption coefficient, and P and P are,
λ λ
–3
respectively, the incident and transmitted spectral radiant power. For l in cm and c in mol dm (M), ε(λ) will result
3 –1 –1 –1 –1 2 –1 3 –1 –1
in dm mol cm (M cm ), a commonly used unit. SI unit of ε(λ) is m mol (10 dm mol cm ).
Note 2 to entry: Spectral radiant power shall be used because the Beer–Lambert law holds only if the spectral
bandwidth of the ultraviolet, visible, or infrared radiation is narrow as compared to spectral linewidths in the
spectrum.
Note 3 to entry: See also absorbance, attenuance, extinction coefficient, Lambert law.
3.24
biphotonic excitation
simultaneous (coherent) absorption of two photons (either same or different wavelength), the energy of
excitation being the sum of the energies of the two photons
Note 1 to entry: Also called two-photon excitation.
Note 2 to entry: This term is sometimes also used for a two-step absorption when the absorption is no longer
simultaneous.
3.25
biphotonic process
resulting from biphotonic excitation
Note 1 to entry: See also multiphoton process.
3.26
bleaching
in photochemistry, this term refers to the loss of absorption or emission intensity
12
==
==
---------------------- Page: 14 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
3.27
blue shift
informal expression for hypsochromic shift
3.28
Brewster angle, θ
B
when an unpolarized planar electromagnetic wavefront impinges on a flat dielectric surface, there is a
unique angle (θ ), commonly referred to as Brewster angle, at which the reflected waves are all polarized
B
into a single plane
1/2
Note 1 to entry: Expression for Brewster angle: θ = arctan (n / n ) = arctan (ε / ε ) where n and n are the
B 2 1 2 1 2 1
refractive indices of the receiving surface and the initial medium, respectively, and ε and ε are the relative static
2 1
permittivities (formerly called dielectric constants).
Note 2 to entry: For a randomly polarized beam incident at Brewster angle, the electric fields of the reflected and
refracted waves are perpendicular to each other.
Note 3 to entry: For a wave incident from air on water (n = 1,333), glass (n = 1,515), and diamond (n = 2,417), the
Brewster angles are 53, 57, and 67,5 degrees, respectively.
3.29
charge recombination
reverse of charge separation
Note 1 to entry: In using this term, it is important to specify the resulting electronic state of the donor and
acceptor.
3.30
charge separation
process in which, under a suitable influence (e.g., photoexcitation), electronic charge moves in a way that
increases (or decreases) the difference in local charges between donor and acceptor sites. Term often
used in photocatalysis as the generated species in the bands of the semiconductor are charged (electrons
and holes)
Note 1 to entry: Charge recombination reduces (or increases) the difference.
Note 2 to entry: Electron transfer between neutral species is the most common example of charge separation. The
most important example of charge recombination is electron backtransfer occurring after photoinduced charge
separation.
3.31
charge shift
under a suitable influence (e.g., photoexcitation), electronic charge moves without changing the absolute
value of the difference in local charges between the original donor and acceptor sites
Note 1 to entry: Prominent examples are the electron transfer reversing the charges in a system composed of a
neutral donor and a cationic acceptor or of a neutral acceptor and an anionic donor.
3.32
charge-transfer (CT) transition
electronic transition in which a large fraction of an electronic charge is transferred from one region of a
molecular entity, called the electron donor, to another, called the electron acceptor (intramolecular CT)
or from one molecular entity to another (intermolecular CT)
Note 1 to entry: Transition typical for donor-acceptor complexes or multichromophoric molecular entities.
13
---------------------- Page: 15 ----------------------
oSIST prEN 16981:2020
prEN 16981:2020 (E)
Note 2 to entry: See also charge-transfer absorption.
3.33
chemiluminescence
luminescence arising from generation by a chemical reaction of electronically excited molecular entities
from reactants in their ground electronic states
3.34
chromophore
part of a molecular entity consisting of an atom or moiety in which the electronic transition responsible
for a given spectral band above 200 nm is approximately localized
Note 1 to entry: In practice, this definition is extended to a part of a molecular entity in which an electronic
transition responsible for absorption in the ultraviolet region of the spectrum is approximately localized as well as
to a part of a molecular entity in which a vibrational, rotational, or bending transition responsible for absorption in
the infrared region of the spectrum is approximately localized.
3.35
CIELAB
a Lab color space is a color-oppon
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.