Rayleigh ratio
Encyclopedia
The Rayleigh ratio is a quantity used to characterize the scattered intensity as a function of scattering angle 
, and is defined as
where
is the intensity of the
incident radiation,
is the total intensity of scattered radiation observed
at an angle
and a distance 
from the point of scattering and 
is the
scattering volume. The factor
is introduced to compensate for polarization phenomena, and is dependent of the type of radiation used as follows:
1. For light scattering
,
depends on the polarization of the incident beam, and is
for vertically polarized light, 
for horizontally polarized light
and
for unpolarized light.
2. For small-angle neutron scattering
,
.
3. For small-angle X-ray scattering
,
, if 
< ~ 5° .
Notes:
1. The dimension of
is an inverse length.
2. In small-angle neutron scattering the term cross-section is frequently used
in place of
.
3. IUPAC
also recommends the symbol
.
, and is defined aswhere
is the intensity of theincident radiation,
is the total intensity of scattered radiation observedat an angle
and a distance from the point of scattering and is thescattering volume. The factor
is introduced to compensate for polarization phenomena, and is dependent of the type of radiation used as follows:1. For light scattering
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
,
depends on the polarization of the incident beam, and is for vertically polarized light, for horizontally polarized lightand
for unpolarized light.2. For small-angle neutron scattering
Neutron scattering
Neutron scattering,the scattering of free neutrons by matter,is a physical processand an experimental technique using this processfor the investigation of materials.Neutron scattering as a physical process is of primordial importance...
,
.3. For small-angle X-ray scattering
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
,
, if < ~ 5° .Notes:
1. The dimension of
is an inverse length.2. In small-angle neutron scattering the term cross-section is frequently used
in place of
.3. IUPAC
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science . The international headquarters of IUPAC is located in Zürich,...
also recommends the symbol
.