ISO 22412:2025

Particle size analysis — Dynamic light scattering (DLS)

This document specifies the application of dynamic light scattering (DLS) to the following: — measurement of average hydrodynamic particle size; — measurement of the size distribution of mainly sub micrometre-sized particles, emulsions or fine bubbles dispersed in liquids. This document is applicable to the measurement of a broad range of dilute and concentrated suspensions.

Analyse granulométrique — Dispersion lumineuse dynamique (DLD)

General Information

• Status: Published
• Publication Date: 04-Sep-2025
• ICS: 19.120 - Particle size analysis. Sieving
• Technical Committee: ISO/TC 24/SC 4 - Particle characterization
• Drafting Committee: ISO/TC 24/SC 4 - Particle characterization
• Current Stage: 6060 - International Standard published
• Start Date: 05-Sep-2025
• Due Date: 17-Aug-2025
• Completion Date: 05-Sep-2025

Relations

• Revises: ISO 22412:2017 - Particle size analysis — Dynamic light scattering (DLS)
• Effective Date: 20-Aug-2022

Standards Content (Sample)

International
Standard
ISO 22412
Third edition
Particle size analysis — Dynamic
2025-09
light scattering (DLS)
Analyse granulométrique — Dispersion lumineuse dynamique (DLD)
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 3
5 Principle . 4
6 Apparatus . 5
7 Test sample preparation . 7
7.1 General .7
7.2 Concentration limits .7
7.3 Checks for concentration suitability .8
8 Measurement procedure . 8
9 Evaluation of results .10
9.1 General .10
9.2 Correlation analysis .11
9.2.1 Cumulants method .11
9.2.2 Distribution calculation algorithms .11
9.3 Frequency analysis . 12
9.4 Multi angle dynamic light scattering (MADLS) . 12
9.4.1 Measurement of an angular-independent particle size distribution . 12
9.4.2 General angular and concentration dependence .14
9.4.3 Measurement of particles with optical anisotropy .14
9.5 Imaging dynamic light scattering (DLS) .14
9.5.1 Image-based dynamic light scattering (IDLS) .14
9.5.2 Ultrafast image-based dynamic light scattering (UIDLS) . 15
10 System qualification and quality control .15
10.1 System qualification . 15
10.2 Quality control of measurement results .16
10.3 Method precision and measurement uncertainty .16
11 Test report . 17
Annex A (informative) Theoretical background . 19
Annex B (informative) Online measurements .33
Annex C (informative) Recommendations for sample preparation .35
Annex D (informative) Guidance on measurement planning, data interpretation and quality
control . 41
Annex E (informative) Guidance on potential measurement artefacts and on ways to minimize
their influence .58
Bibliography . 61

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 24, Particle characterization including sieving,
Subcommittee SC 4, Particle characterization.
This third edition cancels and replaces the second edition (ISO 22412:2017), which has been technically
revised.
The main changes are as follows:
— inclusion of multi-angle dynamic light scattering (MADLS);
— inclusion of imaging dynamic light scattering (DLS);
— addition of Clause A.5 on polarisation-separated backscatter photon cross-correlation spectroscopy;
— extension of Annex B on online measurements;
— incorporation of the content from ISO TR 22814 into Annexes C and D.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Particle size analysis in the sub micrometre size range is performed on a routine basis using the dynamic
light scattering (DLS) technique, which probes the hydrodynamic mobility of the particles. The technique
is successful because it provides estimates of the average particle size and size distribution within a few
minutes, and because user-friendly commercial instruments are available. Nevertheless, proper use of the
instrument and interpretation of the result involve certain precautions.
The principle of DLS for a concentrated suspension is the same as for a dilute suspension. However, specific
requirements for the instrument setup and specification of test sample preparation are specified for
concentrated suspensions. At high concentrations, particle-particle interactions and multiple light scattering
can become dominant and can result in apparent particle sizes that differ between concentrated and dilute
suspensions.
DLS is also referred to as “quasi-elastic light scattering (QELS)” and “photon correlation spectroscopy (PCS),”
although PCS is actually one of the measurement methods.
Several methods have been developed for DLS. These methods can be classified in several ways:
a) by the difference in raw data acquisition (autocorrelation, cross-correlation and frequency analysis,
spatial correlation);
b) by the difference in optical setup (homodyne mode versus heterodyne mode);
c) by the angle of observation.
In addition, instruments show differences with respect to the type of laser source and often allow application
of different data analysis algorithms, e.g. cumulants, non-negative least squares (NNLS), CONTIN, etc.

v
International Standard ISO 22412:2025(en)
Particle size analysis — Dynamic light scattering (DLS)
1 Scope
This document specifies the application of dynamic light scattering (DLS) to the following:
— measurement of average hydrodynamic particle size;
— measurement of the size distribution of mainly sub micrometre-sized particles, emulsions or fine bubbles
dispersed in liquids.
This document is applicable to the measurement of a broad range of dilute and concentrated suspensions.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
particle
minute piece of matter with defined physical boundaries
Note 1 to entry: A physical boundary can also be described as an interface.
Note 2 to entry: A particle can move as a unit.
[SOURCE: ISO 26824:2022, 1.1, modified — Note 3 to entry has been deleted.]
3.2
average hydrodynamic diameter
x
DLS
hydrodynamic diameter that reflects the central value of the underlying particle (3.1) size distribution
Note 1 to entry: The average particle
...

FINAL DRAFT
International
Standard
ISO/FDIS 22412
ISO/TC 24/SC 4
Particle size analysis — Dynamic
Secretariat: BSI
light scattering (DLS)
Voting begins on:
Analyse granulométrique — Dispersion lumineuse dynamique 2025-06-03
(DLD)
Voting terminates on:
2025-07-29
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 22412:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 22412:2025(en)
International
Standard
ISO/FDIS 22412
ISO/TC 24/SC 4
Particle size analysis — Dynamic
Secretariat: BSI
light scattering (DLS)
Voting begins on:
Analyse granulométrique — Dispersion lumineuse dynamique (DLD)
Voting terminates on:
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 22412:2025(en) © ISO 2025

ii
ISO/FDIS 22412:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 3
5 Principle . 4
6 Apparatus . 5
7 Test sample preparation . 7
7.1 General .7
7.2 Concentration limits .7
7.3 Checks for concentration suitability .8
8 Measurement procedure . 9
9 Evaluation of results .10
9.1 General .10
9.2 Correlation analysis .11
9.2.1 Cumulants method .11
9.2.2 Distribution calculation algorithms .11
9.3 Frequency analysis . 12
9.4 Multi angle dynamic light scattering (MADLS) . 12
9.4.1 Measurement of an angular-independent particle size distribution . 12
9.4.2 General angular and concentration dependence .14
9.4.3 Measurement of particles with optical anisotropy .14
9.5 Imaging dynamic light scattering (DLS) .14
9.5.1 Image-based dynamic light scattering (IDLS) .14
9.5.2 Ultrafast image-based dynamic light scattering (UIDLS) . 15
10 System qualification and quality control .15
10.1 System qualification . 15
10.2 Quality control of measurement results .16
10.3 Method precision and measurement uncertainty .16
11 Test report . 17
Annex A (informative) Theoretical background . 19
Annex B (informative) Online measurements .33
Annex C (informative) Recommendations for sample preparation .35
Annex D (informative) Guidance on measurement planning, data interpretation and quality
control . 41
Annex E (informative) Guidance on potential measurement artefacts and on ways to minimize
their influence .57
Bibliography .60

iii
ISO/FDIS 22412:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 24, Particle characterization including sieving,
Subcommittee SC 4, Particle characterization.
This third edition cancels and replaces the second edition (ISO 22412:2017), which has been technically
revised.
The main changes are as follows:
— inclusion of multi-angle dynamic light scattering (DLS);
— inclusion of imaging DLS;
— addition of Clause A.5 on polarisation-separated backscatter photon cross-correlation spectroscopy;
— extension of Annex B on online measurements;
— incorporation of the content from ISO TR 22814 into Annexes C and D.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 22412:2025(en)
Introduction
Particle size analysis in the sub micrometre size range is performed on a routine basis using the dynamic
light scattering (DLS) method, which probes the hydrodynamic mobility of the particles. The technique
is successful because it provides estimates of the average particle size and size distribution within a few
minutes, and because user-friendly commercial instruments are available. Nevertheless, proper use of the
instrument and interpretation of the result involve certain precautions.
The principle of DLS for a concentrated suspension is the same as for a dilute suspension. However, specific
requirements for the instrument setup and specification of test sample preparation are specified for
concentrated suspensions. At high concentrations, particle-particle interactions and multiple light scattering
can become dominant and can result in apparent particle sizes that differ between concentrated and dilute
suspensions.
DLS is also referred to as “quasi-elastic light scattering (QELS)” and “photon correlation spectroscopy (PCS),”
although PCS is actually one of the measurement techniques.
Several methods have been developed for DLS. These methods can be classified in several ways:
a) by the difference in raw data acquisition (autocorrelation, cross-correlation and frequency analysis,
spatial correlation);
b) by the difference in optical setup (homodyne mode versus heterodyne mode);
c) by the angle of observation.
In addition, instruments show differences with respect to the type of laser source and often allow application
of different data analysis algorithms, e.g. cumulants, non-negative least squares (NNLS), CONTIN, etc.

v
FINAL D
...

ISO/FDIS 22412(en)
ISO/TC 24/SC 4
Secretariat: BSI
Date: 2025-03-3105-19
Particle size analysis — Dynamic light scattering (DLS)
Analyse granulométrique — Dispersion lumineuse dynamique (DLD)
FDIS stage
ISO/FDIS 22412:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email:
E-mail: [e-mail]
Formatted: French (Switzerland)
Website: www.iso.org
Field Code Changed
Published in Switzerland.
Formatted: French (Switzerland)
Formatted: French (Switzerland)

ii
ISO/FDIS 22412:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 3
5 Principle . 4
6 Apparatus . 5
7 Test sample preparation . 8
7.1 General . 8
7.2 Concentration limits . 8
7.3 Checks for concentration suitability . 9
8 Measurement procedure . 10
9 Evaluation of results . 11
9.1 General . 11
9.2 Correlation analysis . 12
9.3 Frequency analysis . 13
9.4 Multi angle dynamic light scattering (MADLS) . 14
9.5 Imaging dynamic light scattering (DLS) . 16
10 System qualification and quality control . 17
10.1 System qualification . 17
10.2 Quality control of measurement results . 18
10.3 Method precision and measurement uncertainty . 18
11 Test report . 19
Annex A (informative) Theoretical background . 21
Annex B (informative) Online measurements . 40
Annex C (informative) Recommendations for sample preparation . 42
Annex D (informative) Guidance on measurement planning, data interpretation and quality
control . 49
Annex E (informative) Guidance on potential measurement artefacts and on ways to minimize
their influence . 72
Bibliography . 76

© ISO 2025 – All rights reserved
iii
ISO/FDIS 22412:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 24, Particle characterization including sieving,
Subcommittee SC 4, Particle characterization.
This third edition cancels and replaces the second edition (ISO 22412:2017), which has been technically
revised.
The main changes are as follows:
— — inclusion of multi-angle dynamic light scattering (DLS;);
— — inclusion of imaging DLS;
— — addition of Clause A.5Annex A5 on polarisation-separated backscatter photon cross-correlation
spectroscopy;
— — extension of Annex BAnnex B on online measurements;
— — incorporation of the content offrom ISO TR 22814 “Good practice for Dynamic Light Scattering (DLS)
measurements” as Annex C into Annexes C and DD. ISO/TR 22814 was subsequently withdrawn.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
ISO/FDIS 22412:2025(en)
Introduction
Particle size analysis in the sub micrometre size range is performed on a routine basis using the dynamic light
scattering (DLS) method, which probes the hydrodynamic mobility of the particles. The success of the
technique is successful because it provides estimates of the average particle size and size distribution within
a few minutes, and thatbecause user-friendly commercial instruments are available. Nevertheless, proper use
of the instrument and interpretation of the result involve certain precautions.
The principle of DLS for a concentrated suspension is the same as for a dilute suspension. However, specific
requirements for the instrument setup and specification of test sample preparation are specified for
concentrated suspensions. At high concentrations, particle-particle interactions and multiple light scattering
can become dominant and can result in apparent particle sizes that differ between concentrated and dilute
suspensions.
DLS is also referred to as “quasi-elastic light scattering (QELS)” and “photon correlation spectroscopy (PCS),”
although PCS is actually one of the measurement techniques.
Several methods have been developed for DLS. These methods can be classified in several ways:
a) a) by the difference in raw data acquisition (autocorrelation, cross-correlation and frequency analysis,
spatial correlation);
b) b) by the difference in optical setup (homodyne mode versus heterodyne mode);
c) c) by the angle of observation.
In addition, instruments show differences with respect to the type of laser source and often allow application
of different data analysis algorithms (, e.g. cumulants, non-negative least squares (NNLS,), CONTIN, etc.).
© ISO 2025 – All rights reserved
v
Final Draft International Standard ISO/FDIS 22412(en)

Particle size analysis — Dynamic light scattering (DLS)
1 Scope
This document specifies the application of dynamic light scattering (DLS) to the following:
— —measurement of average hydrodynamic particle size;
— —measurement of the size distribution of mainly sub micrometre-sized particles, emulsions or fine
bubbles dispersed in liquids.
DLS is also referred to as “quasi-elastic light scattering (QELS)” and “photon correlation spectroscopy (PCS),”
although PCS is actually one of the measurement techniques.
This document is applicable to the measurement of a broad range of dilute and concentrated suspensions. The
principle of DLS for a concentrated suspension is the same as for a dilute suspension. However, specific
requirements for the instrument setup and specification of test sample preparation are specified for
concentrated suspensions. At high concentrations, particle-particle interactions and multiple light scattering
can become dominant and can result in apparent particle sizes that differ between concentrated and dilute
suspensions.
2 Normative references
There are no normative references in this document.

53 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminologicalterminology databases for use in standardization at the following
addresses:
— — IEC Electropedia: available at
— — ISO Online browsing platform: available at https://www.iso.org/obp
IEC Electropedia: available at https://www.electropedia.org/3.1
—
3.1
particle
minute piece of matter with defined physical boundaries
Note 1 to entry: A physical boundary can also be described as an interface.
Note 2 to entry: A particle can move as a unit.
ISO/FDIS 22412:2025(en)
[SOURCE: ISO 26824:2022, 1.1, modified — Note 3 to entry has been deleted.]
5.13.2 3.2
average hydrodynamic diameter
𝒙𝒙¯
𝑫𝑫𝑫𝑫𝑫𝑫
hydrodynamic diameter that reflects the central value of the underlying particle (3.1(3.1)) size distribution
Note 1 to entry: The average particle diameter is either directly determined without calculation of the particle size
distribution, or calculated from the computed intensity-, volume- or number-weighted particle size distribution or from
its fitted (transformed) density function. The exact nature of the average particle diameter depends on the evaluation
algorithm.
Note 2 to entry: The cumulants method yields a scattered light intensity-weighted harmonic mean particle diameter,
which is sometimes also referred to as the “z-average diameter.”
Note 3 to entry: Arithmetic, geometric and harmonic mean values can be calculated from the particle size distribution
according to ISO 9276--2.
Note 4 to entry: Mean values calculated from density functions (linear abscissa) and transformed density functions
(logarithmic abscissa) can differ significantly (see ISO 9276--1).
Note 5 to entry: 𝑥𝑥¯ also depends on the particle shape, polydispersity and the scattering vector (and thus on the angle
DLS
of observation, laser wavelength and refractive index of the suspension medium).
Note 6 to entry: The hydrodynamic radius may also be specified.
5.23.3 3.3
polydispersity index
PI
dimensionless measure of the broadness of the size distribution
5.33.4 3.4
scattering volume
volume defined by the intersection of the incident laser beam and the scattered light intercepted by the
detector
5.43.5 3.5
scattered intensity
intensity of the light scattered by the particles (3.1(3.1)) in the scattering volume (3.4(3.4))
5.53.6 3.6
count rate
I
s
number of photon pulses per unit time
N
...