Volume 03 Issue 07-2023
99
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
03
ISSUE
07
Pages:
99-106
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
A
BSTRACT
This work is devoted to the study of physical properties of inelastic scattering of light from different media
as a result of intermolecular interaction. Intermolecular interaction plays a major role in studying the basic
properties and physical nature of substances. In order to study the nature and mechanism of the
intermolecular interaction of liquids, the process of formation of the combined scattering spectra of light,
which is the most effective among various optical methods, and the optical properties were studied.
K
EYWORDS
Inelastic, antistokes, stokes, dipole, polarization, frequency, satellite, monochromatic, concentration,
incoherent.
I
NTRODUCTION
Nowadays, studying the nature of intermolecular
interaction is one of the main tasks of modern
molecular physics. Intermolecular interaction
plays a major role in studying the basic properties
and physical nature of substances. The properties
of substances depend on what molecules it is
made of and how these molecules are arranged
among themselves. Solving many fundamental
problems in the field of physics, chemistry and
biology requires the amount of molecules in
Journal
Website:
http://sciencebring.co
m/index.php/ijasr
Copyright:
Original
content from this work
may be used under the
terms of the creative
commons
attributes
4.0 licence.
Research Article
STUDYING THE PHYSICAL PROPERTIES OF INELASTIC
SCATTERING OF LIGHT FROM MEDIA
Submission Date:
July 18, 2023,
Accepted Date:
July 23, 2023,
Published Date:
July 28, 2023
Crossref doi:
https://doi.org/10.37547/ijasr-03-07-18
I.A. Tolipov
Graduate Student Of Termiz State University, Uzbekistan
M.P. Kholmurodov
Associate Professor Of The General Physics Department Of Termiz State University, Uzbekistan
Volume 03 Issue 07-2023
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VOLUME
03
ISSUE
07
Pages:
99-106
SJIF
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(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
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1368736135
matter, their structure and other properties in a
wide range of temperature, pressure and
concentration and in different aggregate states. In
this respect, applying the achievements of all
sciences to production is one of the urgent
problems of today. Despite the fact that some
progress has been made in creating the statistical
theory of fluids in recent years, many difficulties
are encountered. Due to the widespread use of
liquids in practice and their use in several fields
of chemistry, biology and physics, the demand for
knowledge of the structure and properties of
liquids and the environment is increasing, and as
a result, further development of the theory of
liquids is required. Therefore, the most effective
among various optical methods for studying the
nature and mechanism of intermolecular
interaction of liquids is the method of studying
light combinatory scattering spectra. Optically,
the condition of homogeneity means that the
refractive indices of different parts of the medium
have the same value. When the refractive index of
such a medium is constant in the entire volume, it
is concluded that light refraction phenomena do
not occur. The use of different techniques to
obtain
information
on
intermolecular
interactions using combinational scattering
spectra has been researched for many years and
several works have been done in this field. Many
researchers in this field have explained the
occurrence of various effects observed in these
molecules through various interactions. It should
be noted that the results of scientific research
conducted in this work will further expand our
understanding of liquid environments, contribute
to the rapidly developing field of biotechnology
and
the
development
of
molecular
spectroscopy.In relay scattering, the frequency of
the scattered light corresponds to the frequency
of the incident light. Since Rayleigh was the first
to identify this type of scattering, it is called
Rayleigh scattering. This scattering occurs
coherently. Therefore, Rayleigh scattering is a
coherent scattering of light (Fig.1). However,
careful investigations have shown that in the
spectrum of scattered light, in addition to the
lines characterizing the incident light, there are
additional lines (satellites), which are known to
stand next to each line of incident light. ldi
(Fig.1)[1,2].
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VOLUME
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Figure 1. Transitions between energy levels leading to Rayleigh (
0
) and combinatorial (
0
-
ans
or
0
+
ans
) scattering spectra
Since satellites appear near any spectral line of
incident light, the question arises as to what
conditions these satellites can be observed. In
order for satellites to be visible, the incident light
spectrum must not be a continuous spectrum, but
a set of separate lines (monochromatic lines).
The following laws of this phenomenon have been
found from experience.
• Sa
tellites are near each line of incident light.
• The difference between the frequency of the
spectral line of the exciting (falling) light and the
frequencies of each of the lines from the satellites
....,is characteristic for the scattering
substance and is equal to the specific vibrational
frequencies of its molecules
:
• Satellites consist of two systems of lines lying
symmetrically on both sides of the wake line,
(Fig.1) i.e.
Here, on the left a re the frequencies of the
satellites on the longer wavelength side than the
excitation frequencies, and on the right are the
frequencies of the satellites on the other side of
the excitation frequencies.The first satellites,
which are located near the red part of the
spectrum and are therefore called "red" satellites,
are much more intense than "violet" satellites
(Fig.1) [1,3,4].
• When the temperature rises, the intensity of
"purple" satellites increases rapidly.
'
"
,
"
,
'
v
v
v
( )
i
v
,...
''
'
,
''
,
'
3
0
3
2
0
2
1
0
1
i
i
i
v
v
v
v
v
v
v
v
v
v
v
v
=
−
=
=
−
=
=
−
=
.
0
0
v
v
v
r
−
=
−
Volume 03 Issue 07-2023
102
International Journal of Advance Scientific Research
(ISSN
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2750-1396)
VOLUME
03
ISSUE
07
Pages:
99-106
SJIF
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FACTOR
(2021:
5.478
)
(2022:
5.636
)
(2023:
6.741
)
OCLC
–
1368736135
Combined scattering was first discovered by G.S.
Landsberg and L.I. Mandelstam and Indian
scientists Raman and Krishnan. Indian scientists
won the Nobel Prize. In foreign literature, this
process is also called the Raman effect. This
scattering is commonly called combinatorial
scattering.
Classical theory of combinatorial scattering of
light
The phenomenon of combinatorial scattering is
explained in terms of classical theory as follows.
The reasons for the appearance of satellites in this
phenomenon can be explained by the modulation
by low-frequency vibrations of the atoms of the
molecules of the light wave scattering medium.
Polarization of a molecule generally depends on
the location of the atoms that make it up. When
atoms vibrate, the polarization
0
- oscillates
around the average value, which can be explained
as follows:
The frequency of these vibrations is 10
12
-10
13
Hz
and corresponds to the infrared spectrum of the
electromagnetic wave scale. In other words, the
magnitude change of
(t)
changes more slowly
compared to the fluctuation of the
(
)
Gr
15
10
electric field of the incident light. For this reason,
the change in the dipole moment of the molecule
in the monochromatic field of the incident light
wave
occurs according to the law, that is, it consists of
amplitude modulated oscillation. Here is the
- variable electric field of the light
wave,
Е
0
is the amplitude of the electric field
intensity of the light wave, is the angular
frequency
-of the incident light,
- is the
polarizability of the molecule, which depends
only on its structure and properties l is a constant.
In this process, the oscillation of the scattered
light field strength is also modulated. The carrier
frequency - of these vibrations is equal
-to
the frequency of the incident light wave, and the
modulation occurs at - frequencies (vibration
frequency of the atoms in the molecule of the
scattering substance). The spectrum of such
amplitude-modulated oscillations
-along
with the frequency carrier frequency, combined
oscillations with a frequency are formed. In other
words, the spectrum of the scattered light gives
information about this molecule. By studying and
analyzing this spectrum, we will be able to know
the structure and structure of the molecule[4,5].
According to the classical law
of
electrodynamics, the intensity of a dipole
oscillating at a frequency
(1)
emits monochromatic light equal to
for example, that is, if the polarizability
of the molecule of the scattering medium changes,
then the dipole moment of the molecule also
changes over time. In general, the polarizability of
a molecule should vary due to the participation of
the nuclear vibration in dipole vibrations. Due to
the interconnectedness of electrons and the
nucleus, the electrons oscillating at a forced
frequency cause the nucleus to vibrate as well.
( )
( )
t
E
t
F
E
t
p
cos
0
0
+
=
=
t
Е
Е
cos
0
=
v
2
=
i
i
v
2
=
2
0
2
2
4
4
3
16
E
c
v
I
v
=
сonst
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(ISSN
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VOLUME
03
ISSUE
07
Pages:
99-106
SJIF
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(2021:
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)
(2022:
5.636
)
(2023:
6.741
)
OCLC
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1368736135
However, since the mass of the nucleus is very
large compared to the mass of the electron, the
vibration of the nucleus is very weak. This causes
the polarity of the molecule to change. As a result,
the frequency of the scattered light changes and
the displacement becomes incoherent .
Thus, classical electrodynamics correctly explains
the appearance of lines - satellites symmetrically
shifted by a distance i on both sides of the
unshifted line ( ) in the spectrum
i
- of
scattered light, and their intensity
( )
(
)
2
0
4
4
0
2
4
2
0
4
4
,
2
4
,
3
4
3
4
E
c
E
c
I
i
A
S
R
A
S
=
=
(2)
is calculated by the formula. In this
- the
Raman frequency (for Stokes and anti-Stokes
lines). From the point of view of classical
electrodynamics, it follows that the intensity of
Stokes and anti-Stokes lines is equal. It is known
from the results of the experiment that the
intensity of these lines (satellites) is not equal,
including that the intensity of red satellites-
Stokes lines is higher than the intensity of purple
satellites. Classical physics could not explain this
quantitative difference between the intensities of
red and violet satellites. The quantitative problem
of intensities in combinatorial scattering of light
can be correctly explained only on the basis of
quantum concepts.
Quantum theory of combinatorial scattering
of light
Using a simplified view of light quanta, it is
possible to understand the essence of the
phenomenon of combinatorial scattering.
According to quantum views, light with a
frequency is scattered in the form
of certain
fractions (quanta), the amount
of which is
equal to where
J.s (s - Planck is a
universal constant. Therefore, an atom with
frequency oscillations has a reserve of energy.
This energy can be emitted by the atom in the
form
of light with such a frequency. From
this point of view, the scattering of light in
molecules by light quanta ( (that is, photons)
collide with molecules. As a result of this collision,
the photons change their direction. Collisions
between photons and molecules are elastic and
inelastic. The collision is an elastic collision. in the
case of collision, the energy of the molecule and
the frequency of the photon do not change, which
corresponds to Rayleigh scattering (Fig.1). That is
why Rayleigh scattering is also called elastic
scattering[5].
If the collision is inelastic, the energy of the
photon changes by the amount of the oscillating
quantum. If light interacts with a molecule that is
not in a vibrational state, the light gives the
molecule the appropriate part of its energy,
according to the equation
h
=h
0
-h
i
or
=
0
-
i
turns into a low-frequency light (red satellite,
Stokes line), where the frequency
of the
excitation light is the frequency
of the
molecule's vibrations. If light affects a molecule in
a state of vibration, i.e.,
-a molecule with
energy, then the light absorbs this energy from
the
molecule,
or
,
A
S
R
v
,
0
v
0
hv
34
10
62
,
6
−
=
h
0
hv
0
v
i
v
i
hv
i
hv
hv
hv
+
=
0
'
i
v
v
v
+
=
0
'
Volume 03 Issue 07-2023
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VOLUME
03
ISSUE
07
Pages:
99-106
SJIF
I
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(2021:
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)
(2022:
5.636
)
(2023:
6.741
)
OCLC
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1368736135
according to the equation, to high-frequency light
(Violet satellite, anti-Stokes line becomes).This
can be easily understood from Figure 1 above.
Based on the above, combinatorial scattering can
be defined as follows: The frequency of the
scattered light is composed of the combination
of the frequency of the incident light and the
frequency
of vibrations inside the molecules.
Therefore, this scattering is called combinatorial
scattering.The number of molecules in a state of
vibration is much less than the number of
unexcited molecules, so the intensity of the violet
satellite must be incomparably less than the
intensity of the red satellite; the same is true in
experience. As the temperature rises, the number
of excited molecules increases rapidly, so the
intensity of purple satellites should increase
rapidly; this is also confirmed in experience.In
fact, the intensity of the combinational line with a
frequency is determined by how much the
polarizability of the molecule changes when the
molecule vibrates corresponding to this
frequency. The change of the electric moment
with the change of polarity can be expressed in
different ways in different oscillations[5,6].
Vibrations that are active in the infrared
spectrum are not active in the combined
scattering spectrum and vice versa. In SO
2
a
different vibration (Fig.2,v), the polarity does not
change, because when one of the oxygen atoms
approaches the carbon, the other moves away
and vice versa; however, the electric moment (O)
of the molecule changes during these
vibrations.Therefore, in the first type of
oscillation (Fig.2b), a combinatorial scattering
line appears, the frequency (O) of this line can be
determined from the combinatorial scattering
spectrum;
Figure 2. Types of atomic vibration in the SO2 molecule. initial situation of a-atoms; b-polarization
changing vibration; v-electric torquechanging vibration.
In the second type of vibration (Fig.2b), the
frequency can be found depending on the position
of
the
infrared
absorption
band.The
combinational scattering method is an important
method for studying the molecular structure of a
substance[2,4,6]. The specific frequencies
0
v
i
v
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VOLUME
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of molecular vibrations are easily determined
using this method; this method allows us to think
about the nature of molecular symmetry, the
magnitude of the forces acting inside the
molecules, and the specific aspects of molecular
dynamics in general.In many cases, this method is
studied together with the infrared absorption
method, which allows for a complete study of the
molecule. Combination scattering spectra are so
characteristic of molecules that complex
molecular mixtures can be analyzed with the help
of these spectra, especially mixtures of organic
molecules that are difficult or even impossible to
analyze by chemical means. For example, the
composition of gasoline, which is a very complex
mixture of hydrocarbons, is effectively analyzed
using the combinatorial scattering method.
Above, we talked about combinatorial scattering,
which occurs during the interaction of primary
radiation with molecules of the environment. A
similar phenomenon occurs when light is
scattered by atoms or ions. In order to
understand the essence of the matter, it is
necessary to recall the results of the study of
absorption and dispersion of light in atomic gases.
An atom can be thought of as a set of oscillators;
the specific frequencies of these oscillators are
determined by the difference between the
energies of two arbitrary quantum states of the
atom. Therefore, the difference between atoms
and molecules is only in the nature of oscillators:
oscillators in the form of molecules describe the
movement of nuclei, and in the case of atoms,
oscillators describe the movement of electrons.
Given this similarity, the above considerations
can be applied to atoms from the point of view of
the classical modulation picture and from the
point of view of the simplified quantum
scheme.Inelastic scattering of photons was
predicted theoretically based on their interaction
with atoms (A. Smekal 1923). However, this
phenomenon was found experimentally long
after molecular combinatorial scattering.The
phenomenon of combinatorial scattering of light
can be explained within the framework of
classical physics, but its quantum interpretation
essentially confirms the quantum nature of light.
The combinatorial scattering method is of great
practical importance in the study of the structure
of
molecules,
internal
molecular
and
intermolecular forces, the analysis of complex
mixtures and the identification (separation) of
certain compounds [3,5,6].
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Pages:
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