This appeared on FEb 23rd 2016 in SPECTRUM DECCAN HERALD
RAMAN
EFFECT - THEN AND NOW
Palahalli
R Vishwanath
(The
latest use of this phenomenon is in space exploration )
"
Chandrasekhara Venkata Raman, Nobel-laureate (Physics-1930), assisted
by K S Krishnan at IACS, Calcutta, India, discovered on 28 February
1928, that when a beam of coloured light entered a liquid, a fraction
of the light scattered was of a different colour, dependent on
material property. This radiation effect of molecular scattering of
light bears his name as ‘Raman Effect’. This is the plaque which
greets visitors to the Indian Association for Cultivation of Science
at Jadavpur, Kolkatta. Thus 28th February 1928 is a golden day
for Indian science.
Raman
Effect can be easily understood if the incident light is treated as
consisting of particles called photons. Most of the encounters of
the particles with the target are what is called elastic scattering
where there is no change in energy. However, in few encounters, the
energy of the photon is changed by either giving energy or taking
energy from the molecule Thus the scattered light will have a
frequency (and colour) different than that of the incident light.
Since the phenomenon can be understood with only the photonic aspect
of light , this effect was also seen as one of the proofs for the
quantum theory. Two year later along with S. Bhagavantham Professor
Raman was able to show that "the light quantum possesses an
intrinsic spin equal to one Bohr unit of angular momentum" which
further confirmed the quantum nature of light
Professor Raman , who was born in 1888, started
working in Kolkata in 1907 as a civil servant. Because of his passion
in physics, he started doing experimental work in the Indian
Association for Cultivation of Science. He took up a professorship in
Calcutta University in 1917 where he worked for 15 years. Later he
served as the director of the Indian Institute of Science in
Bangalore from 1934 to 1948 and of the Raman Research Institute
from 1949 until his death in 1970, at the age of 82.
His
early work was in acoustics of musical instruments. In 1924 he was
elected a Fellow of the Royal Society ' for his considerable
additions to our knowledge of sound and light'. He was
— only
the fourth Indian so honored. He received the Nobel Prize in physics
in 1930. In his later years he became interested in the structure of
crystals, especially diamonds.. Educated entirely in India, Raman
did outstanding work at a time when there was practically no research
in the country . He was famous for his lectures " holding the
audience spellbound with his booming voice, lively demonstrations,
superb diction and rich humor". S. Ramasehan's statement ' I
have never seen anyone who enjoyed science so much' sums up this
great man. Raman was the paternal uncle of Subrahmanyan
Chandrasekhar who later won the Nobel Prize in Physics (1983) for
his research in astrophysics
Prof. Raman stated in his Nobel address" ..
enables us to obtain an insight into the ultimate structure of the
scattering substance" which made possible the numerous
applications of Raman effect. The unique spectrum of Raman scattered
light for any particular substance serves as a "fingerprint"
that could be used for qualitative analysis of solids,liquids gases
and even a mixture of materials. Further, the intensity of the
spectral lines is related to the amount of the substance. It is a
ubiquitous technique, giving information on what and how much is
present in a variety of samples. While generally only one part in a
thousand of the total intensity of incident light is Rayleigh
scattered, this value drops to one part in a million for Raman
scattering . Because of this Prof Raman was also aware of the need
for more intense light sources to amplify the effect and observation
of the scattered light. The laser provided this very much needed
intense source of light. Thus the phenomenon t has become more
prominent in the years since powerful monochromatic laser sources
could provide the scattering power. Since lasers are highly
monochromatic it is very helpful in observing even very small
shifts. Further the use of selective filters allows only the
components of inelastic scattering.
i
From
1980s with improved instrumentation many new applications for Raman
effect have been found. Its ability to detect even very small
amounts of chemical and biological molecules has been helpful in
treatment of cancer, malaria, HIV and other illnesses. It now has
varied uses like (a) analyze nuclear waste material from a safe
distance (b) detect trace amounts of molecules in fraudulent
paintings, chemical weapons etc.(c) to identify
dangerous substances such as improvised explosive devices at
airports (d) other defense applications to identify potential
threats and hazards (e) food technology etc
RAMAN
EFFECT - THEN AND NOW
Palahalli
R Vishwanath
(The
latest use of this phenomenon is in space exploration )
"
Chandrasekhara Venkata Raman, Nobel-laureate (Physics-1930), assisted
by K S Krishnan at IACS, Calcutta, India, discovered on 28 February
1928, that when a beam of coloured light entered a liquid, a fraction
of the light scattered was of a different colour, dependent on
material property. This radiation effect of molecular scattering of
light bears his name as ‘Raman Effect’. This is the plaque which
greets visitors to the Indian Association for Cultivation of Science
at Jadavpur, Kolkatta. Thus 28th February 1928 is a golden day
for Indian science.
Raman
Effect can be easily understood if the incident light is treated as
consisting of particles called photons. Most of the encounters of
the particles with the target are what is called elastic scattering
where there is no change in energy. However, in few encounters, the
energy of the photon is changed by either giving energy or taking
energy from the molecule Thus the scattered light will have a
frequency (and colour) different than that of the incident light.
Since the phenomenon can be understood with only the photonic aspect
of light , this effect was also seen as one of the proofs for the
quantum theory. Two year later along with S. Bhagavantham Professor
Raman was able to show that "the light quantum possesses an
intrinsic spin equal to one Bohr unit of angular momentum" which
further confirmed the quantum nature of light
Professor Raman , who was born in 1888, started
working in Kolkata in 1907 as a civil servant. Because of his passion
in physics, he started doing experimental work in the Indian
Association for Cultivation of Science. He took up a professorship in
Calcutta University in 1917 where he worked for 15 years. Later he
served as the director of the Indian Institute of Science in
Bangalore from 1934 to 1948 and of the Raman Research Institute
from 1949 until his death in 1970, at the age of 82.
His
early work was in acoustics of musical instruments. In 1924 he was
elected a Fellow of the Royal Society ' for his considerable
additions to our knowledge of sound and light'. He was
— only
the fourth Indian so honored. He received the Nobel Prize in physics
in 1930. In his later years he became interested in the structure of
crystals, especially diamonds.. Educated entirely in India, Raman
did outstanding work at a time when there was practically no research
in the country . He was famous for his lectures " holding the
audience spellbound with his booming voice, lively demonstrations,
superb diction and rich humor". S. Ramasehan's statement ' I
have never seen anyone who enjoyed science so much' sums up this
great man. Raman was the paternal uncle of Subrahmanyan
Chandrasekhar who later won the Nobel Prize in Physics (1983) for
his research in astrophysics
Prof. Raman stated in his Nobel address" ..
enables us to obtain an insight into the ultimate structure of the
scattering substance" which made possible the numerous
applications of Raman effect. The unique spectrum of Raman scattered
light for any particular substance serves as a "fingerprint"
that could be used for qualitative analysis of solids,liquids gases
and even a mixture of materials. Further, the intensity of the
spectral lines is related to the amount of the substance. It is a
ubiquitous technique, giving information on what and how much is
present in a variety of samples. While generally only one part in a
thousand of the total intensity of incident light is Rayleigh
scattered, this value drops to one part in a million for Raman
scattering . Because of this Prof Raman was also aware of the need
for more intense light sources to amplify the effect and observation
of the scattered light. The laser provided this very much needed
intense source of light. Thus the phenomenon t has become more
prominent in the years since powerful monochromatic laser sources
could provide the scattering power. Since lasers are highly
monochromatic it is very helpful in observing even very small
shifts. Further the use of selective filters allows only the
components of inelastic scattering.
i
From
1980s with improved instrumentation many new applications for Raman
effect have been found. Its ability to detect even very small
amounts of chemical and biological molecules has been helpful in
treatment of cancer, malaria, HIV and other illnesses. It now has
varied uses like (a) analyze nuclear waste material from a safe
distance (b) detect trace amounts of molecules in fraudulent
paintings, chemical weapons etc.(c) to identify
dangerous substances such as improvised explosive devices at
airports (d) other defense applications to identify potential
threats and hazards (e) food technology etc
Raman
effect is also playing an important role in astronomy . The
feasibility of using the Raman spectrum to investigate the physical
structure of outer planet atmospheres has been examined . Raman
scattering makes contribution to spectra because of very large
amounts of hydrogen molecules in their atmosphere. . The spectra
of Uranus and Neptune in the UV and visual range have been detected
and these observations give information on the amount of
hydrocarbons in the atmosphere Similar methods can hopefully be used
for exoplanets also
In
2004, a journal devoted to spectroscopy devoted its special issue
to Raman
spectroscopy breaking terrestrial barriers
. Raman spectroscopy can provide highly specific chemical
fingerprints of inorganic and organic materials and is therefore
expected to play a significant role in interplanetary missions,
especially for the search for life elsewhere in our solar system. In
Raman spectra, the peaks of minerals and molecular bonds are very
sharp and well separated from each other, which enable direct mineral
identification from raw Raman spectra. The simplicity in Raman
spectra and the non-ambiguity for phase identification are the keys
for its application in planetary explorations. Future planetary
missions of NASA and ESA to Europa and Mars are all expected to
carry Raman spectrometers.. A Raman spectrometer is now being
miniaturized for the Exo Mars Rover and is expected to identify
organic compounds that could be related to signatures of life
like cyanobacteria, chlorophyll, or amino acids, It is also
expected to provide a general mineralogical overview,
especially those minerals produced by water‐related
processes. NASA's mission to Europa, an important satellite of
Jupiter, will try to analyze the surface environment and Raman
spectra will be an important contribution to the measurements of the
key habitability parameters, such as temperature, pH etc. Remote
Raman measurements conducted at the University of Hawaii were able to
identify minerals under high temperatures such as those that exist on
the surface of Venus demonstrating the ability of the remote Raman
system to identify atmospheric constituents without landing on the
harsh Venusian surface.
------------------------------------------------------------------------------------------------------------------------
1.
The original apparatus used by Raman
2.
The schematic of the Raman effect : Incident light with a frequency
Fo gets changed to Fo +/- Fm
3.
A Raman spectrometer to be used on Mars is undergoing checks
Raman
effect is also playing an important role in astronomy . The
feasibility of using the Raman spectrum to investigate the physical
structure of outer planet atmospheres has been examined . Raman
scattering makes contribution to spectra because of very large
amounts of hydrogen molecules in their atmosphere. . The spectra
of Uranus and Neptune in the UV and visual range have been detected
and these observations give information on the amount of
hydrocarbons in the atmosphere Similar methods can hopefully be used
for exoplanets also
In
2004, a journal devoted to spectroscopy devoted its special issue
to Raman
spectroscopy breaking terrestrial barriers
. Raman spectroscopy can provide highly specific chemical
fingerprints of inorganic and organic materials and is therefore
expected to play a significant role in interplanetary missions,
especially for the search for life elsewhere in our solar system. In
Raman spectra, the peaks of minerals and molecular bonds are very
sharp and well separated from each other, which enable direct mineral
identification from raw Raman spectra. The simplicity in Raman
RAMAN
EFFECT - THEN AND NOW
Palahalli
R Vishwanath
(The
latest use of this phenomenon is in space exploration )
"
Chandrasekhara Venkata Raman, Nobel-laureate (Physics-1930), assisted
by K S Krishnan at IACS, Calcutta, India, discovered on 28 February
1928, that when a beam of coloured light entered a liquid, a fraction
of the light scattered was of a different colour, dependent on
material property. This radiation effect of molecular scattering of
light bears his name as ‘Raman Effect’. This is the plaque which
greets visitors to the Indian Association for Cultivation of Science
at Jadavpur, Kolkatta. Thus 28th February 1928 is a golden day
for Indian science.
Raman
Effect can be easily understood if the incident light is treated as
consisting of particles called photons. Most of the encounters of
the particles with the target are what is called elastic scattering
where there is no change in energy. However, in few encounters, the
energy of the photon is changed by either giving energy or taking
energy from the molecule Thus the scattered light will have a
frequency (and colour) different than that of the incident light.
Since the phenomenon can be understood with only the photonic aspect
of light , this effect was also seen as one of the proofs for the
quantum theory. Two year later along with S. Bhagavantham Professor
Raman was able to show that "the light quantum possesses an
intrinsic spin equal to one Bohr unit of angular momentum" which
further confirmed the quantum nature of light
Professor Raman , who was born in 1888, started
working in Kolkata in 1907 as a civil servant. Because of his passion
in physics, he started doing experimental work in the Indian
Association for Cultivation of Science. He took up a professorship in
Calcutta University in 1917 where he worked for 15 years. Later he
served as the director of the Indian Institute of Science in
Bangalore from 1934 to 1948 and of the Raman Research Institute
from 1949 until his death in 1970, at the age of 82.
His
early work was in acoustics of musical instruments. In 1924 he was
elected a Fellow of the Royal Society ' for his considerable
additions to our knowledge of sound and light'. He was
— only
the fourth Indian so honored. He received the Nobel Prize in physics
in 1930. In his later years he became interested in the structure of
crystals, especially diamonds.. Educated entirely in India, Raman
did outstanding work at a time when there was practically no research
in the country . He was famous for his lectures " holding the
audience spellbound with his booming voice, lively demonstrations,
superb diction and rich humor". S. Ramasehan's statement ' I
have never seen anyone who enjoyed science so much' sums up this
great man. Raman was the paternal uncle of Subrahmanyan
Chandrasekhar who later won the Nobel Prize in Physics (1983) for
his research in astrophysics
Prof. Raman stated in his Nobel address" ..
enables us to obtain an insight into the ultimate structure of the
scattering substance" which made possible the numerous
applications of Raman effect. The unique spectrum of Raman scattered
light for any particular substance serves as a "fingerprint"
that could be used for qualitative analysis of solids,liquids gases
and even a mixture of materials. Further, the intensity of the
spectral lines is related to the amount of the substance. It is a
ubiquitous technique, giving information on what and how much is
present in a variety of samples. While generally only one part in a
thousand of the total intensity of incident light is Rayleigh
scattered, this value drops to one part in a million for Raman
scattering . Because of this Prof Raman was also aware of the need
for more intense light sources to amplify the effect and observation
of the scattered light. The laser provided this very much needed
intense source of light. Thus the phenomenon t has become more
prominent in the years since powerful monochromatic laser sources
could provide the scattering power. Since lasers are highly
monochromatic it is very helpful in observing even very small
shifts. Further the use of selective filters allows only the
components of inelastic scattering.
i
From
1980s with improved instrumentation many new applications for Raman
effect have been found. Its ability to detect even very small
amounts of chemical and biological molecules has been helpful in
treatment of cancer, malaria, HIV and other illnesses. It now has
varied uses like (a) analyze nuclear waste material from a safe
distance (b) detect trace amounts of molecules in fraudulent
paintings, chemical weapons etc.(c) to identify
dangerous substances such as improvised explosive devices at
airports (d) other defense applications to identify potential
threats and hazards (e) food technology etc
Raman
effect is also playing an important role in astronomy . The
feasibility of using the Raman spectrum to investigate the physical
structure of outer planet atmospheres has been examined . Raman
scattering makes contribution to spectra because of very large
amounts of hydrogen molecules in their atmosphere. . The spectra
of Uranus and Neptune in the UV and visual range have been detected
and these observations give information on the amount of
hydrocarbons in the atmosphere Similar methods can hopefully be used
for exoplanets also
In
2004, a journal devoted to spectroscopy devoted its special issue
to Raman
spectroscopy breaking terrestrial barriers
. Raman spectroscopy can provide highly specific chemical
fingerprints of inorganic and organic materials and is therefore
expected to play a significant role in interplanetary missions,
especially for the search for life elsewhere in our solar system. In
Raman spectra, the peaks of minerals and molecular bonds are very
sharp and well separated from each other, which enable direct mineral
identification from raw Raman spectra. The simplicity in Raman
spectra and the non-ambiguity for phase identification are the keys
for its application in planetary explorations. Future planetary
missions of NASA and ESA to Europa and Mars are all expected to
carry Raman spectrometers.. A Raman spectrometer is now being
miniaturized for the Exo Mars Rover and is expected to identify
organic compounds that could be related to signatures of life
like cyanobacteria, chlorophyll, or amino acids, It is also
expected to provide a general mineralogical overview,
especially those minerals produced by water‐related
processes. NASA's mission to Europa, an important satellite of
Jupiter, will try to analyze the surface environment and Raman
spectra will be an important contribution to the measurements of the
key habitability parameters, such as temperature, pH etc. Remote
Raman measurements conducted at the University of Hawaii were able to
identify minerals under high temperatures such as those that exist on
the surface of Venus demonstrating the ability of the remote Raman
system to identify atmospheric constituents without landing on the
harsh Venusian surface.
------------------------------------------------------------------------------------------------------------------------
1.
The original apparatus used by Raman
2.
The schematic of the Raman effect : Incident light with a frequency
Fo gets changed to Fo +/- Fm
3.
A Raman spectrometer to be used on Mars is undergoing checks
spectra and the non-ambiguity for phase identification are the keys
for its application in planetary explorations. Future planetary
missions of NASA and ESA to Europa and Mars are all expected to
carry Raman spectrometers.. A Raman spectrometer is now being
miniaturized for the Exo Mars Rover and is expected to identify
organic compounds that could be related to signatures of life
like cyanobacteria, chlorophyll, or amino acids, It is also
expected to provide a general mineralogical overview,
especially those minerals produced by water‐related
processes. NASA's mission to Europa, an important satellite of
Jupiter, will try to analyze the surface environment and Raman
spectra will be an important contribution to the measurements of the
key habitability parameters, such as temperature, pH etc. Remote
Raman measurements conducted at the University of Hawaii were able to
identify minerals under high temperatures such as those that exist on
the surface of Venus demonstrating the ability of the remote Raman
system to identify atmospheric constituents without landing on the
harsh Venusian surface.
------------------------------------------------------------------------------------------------------------------------
1.
The original apparatus used by Raman
2.
The schematic of the Raman effect : Incident light with a frequency
Fo gets changed to Fo +/- Fm
3.
A Raman spectrometer to be used on Mars is undergoing checks
