This document provides an overview of coherent anti-Stokes Raman spectroscopy (CARS). It begins with an introduction to CARS and its history. The theoretical background of CARS is then explained, including the basics of Rayleigh and Raman scattering. The document outlines the CARS process, advantages and limitations of CARS, and applications. It concludes with a summary of the key points regarding CARS spectroscopy.
It contains the basic principle of Mossbauer Spectroscopy.
Recoil energy, Dopler shift.
The instrumentation of Mossbauer Spectroscopy.
Hyperfine interactions.
Electron Spin Resonance (ESR) SpectroscopyHaris Saleem
Electron Spin Resonance Spectroscopy
Also called EPR Spectroscopy
Electron Paramagnetic Resonance Spectroscopy
Non-destructive technique
Applications
Extensively used in transition metal complexes
Deviated geometries in crystals
It contains the basic principle of Mossbauer Spectroscopy.
Recoil energy, Dopler shift.
The instrumentation of Mossbauer Spectroscopy.
Hyperfine interactions.
Electron Spin Resonance (ESR) SpectroscopyHaris Saleem
Electron Spin Resonance Spectroscopy
Also called EPR Spectroscopy
Electron Paramagnetic Resonance Spectroscopy
Non-destructive technique
Applications
Extensively used in transition metal complexes
Deviated geometries in crystals
For UG students of All Engineering Branches (Mechanical Engg., Chemical Engg., Instrumentation Engg., Food Technology) and PG students of Chemistry, Physics, Biochemistry, Pharmacy
The link of the video lecture at YouTube is
https://www.youtube.com/watch?v=t3QDG8ZIX-8
A ppt compiled by Yaseen Aziz Wani pursuing M.Sc Chemistry at University of Kashmir, J&K, India and Naveed Bashir Dar, a student of electrical engg. at NIT Srinagar.
Warm regards to Munnazir Bashir also for providing us with refreshing tea while we were compiling ppt.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
These are chemical shift reagents and solvent induced shifts have their application in resolving the NMR Spectra of complex structures by inducing shift with respect to reference compound. Thus useful in interpretation of structures of complex organic compounds.
It contains what are the shift reagents, and how they will use in NMR spectroscopy. It includes lanthanide shift reagents and their effect using NMR spectroscopy. It has mostly used shift reagents like Europium and their importance. paramagnetic species that affect the NMR spectra are also explained in detail. What are contact shift and pseudo-contact shift also explained. It contains what are the chiral shift reagent, and the advantages, and disadvantages of lanthanide shift reagents. Reference books are also included.
NQR - DEFINITION - ELECTRIC FIELD GRADIENT - NUCLEAR QUADRUPOLE MOMENT - NUCLEAR QUADRUPOLE COUPLING CONSTANT - PRINCIPLE OF NQR - ENERGY OF INTERACTION - SELECTION RULE - FREQUENCY OF TRANSITION - APPLICATIONS
For UG students of All Engineering Branches (Mechanical Engg., Chemical Engg., Instrumentation Engg., Food Technology) and PG students of Chemistry, Physics, Biochemistry, Pharmacy
The link of the video lecture at YouTube is
https://www.youtube.com/watch?v=t3QDG8ZIX-8
A ppt compiled by Yaseen Aziz Wani pursuing M.Sc Chemistry at University of Kashmir, J&K, India and Naveed Bashir Dar, a student of electrical engg. at NIT Srinagar.
Warm regards to Munnazir Bashir also for providing us with refreshing tea while we were compiling ppt.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
These are chemical shift reagents and solvent induced shifts have their application in resolving the NMR Spectra of complex structures by inducing shift with respect to reference compound. Thus useful in interpretation of structures of complex organic compounds.
It contains what are the shift reagents, and how they will use in NMR spectroscopy. It includes lanthanide shift reagents and their effect using NMR spectroscopy. It has mostly used shift reagents like Europium and their importance. paramagnetic species that affect the NMR spectra are also explained in detail. What are contact shift and pseudo-contact shift also explained. It contains what are the chiral shift reagent, and the advantages, and disadvantages of lanthanide shift reagents. Reference books are also included.
NQR - DEFINITION - ELECTRIC FIELD GRADIENT - NUCLEAR QUADRUPOLE MOMENT - NUCLEAR QUADRUPOLE COUPLING CONSTANT - PRINCIPLE OF NQR - ENERGY OF INTERACTION - SELECTION RULE - FREQUENCY OF TRANSITION - APPLICATIONS
Với thiết bị quang phổ cầm tay Mira bạn có thể thu được các thông số hóa học một cách nhanh nhất của các mẫu chưa biết trước. Chỉ cần vài giây, thiết bị phân tích cầm tay cung cấp cho bạn kết quả với độ tin cậy cao, phân tích kết quả một cách dễ dàng, cho phép kiểm tra nguyên liệu đầu vào hoặc xác định chất lượng hàng hóa.
Kết quả có độ lặp lại cao ngay các mẫu có thành phần phức tạp nhờ vào kỹ thuật Orbital-Raster-Scan(ORS)
Độ linh hoạt cao – “Thư Viện Mở” đảm bảo kết quả có độ tin cậy cao nhất
Giảm kích thước tới tối đa – Cầm tay, thiết kế compact
Thông tin chi tiết tại Website: http://metrohmhoay.gianhangvn.com/quang-pho-cam-tay-mira-3-806268.html
Raman Spectroscopy is a non destructive chemical analysis technique which provides detailed information about chemical structure, crystallinity and molecular interactions. The raman effect involves scattering of light by molecules of gases, liquids, or solids. Raman Spectroscopy is sensitive to homo-nuclear molecular bonds. It is able to distinguish between single, double, and triple bonds between carbon atoms.Raman spectroscopy is the study of matter by the inelastic scattering of monochromatic
light. It has become a ubiquitous tool in modern spectroscopy, biophysics, microscopy, geochemistry, and analytical chemistry. In contrast to typical absorption or emission spectroscopy experiments, transitions among quantum levels of atoms or molecules are induced by the absorption or emission of photons (IR, visible, UV). In a typical Raman experiment, a polarized monochromatic light source (usually a laser) is focused into a sample, and the scattered light at 90 degree
to the laser beam is collected and dispersed by a high-resolution monochromator. The incident laser wavelength (chosen such that
the sample does not absorb, in ordinary Raman Spectroscopy) is fixed, and the scattered light is
dispersed and detected to obtain the frequency spectrum of the scattered light. The scattered light is very weak
(<10-7 of the incident power), so that monochromators with excellent straylight rejection and sensitive detectors are required. In a much rarer event (approximately 1 in 10million photons)Raman scattering occurs, which is an inelastic scattering process with a transfer of energy between the molecule and scattered photon. If the molecule gains energy from the photon during the scattering (excited to a higher
vibrational level) then the scattered photon loses energy and its wavelength increases which is called Stokes Raman scattering . Inversely, if the molecule loses energy by relaxing to alower vibrational level the scattered photon gains thecorresponding energy and its wavelength decreases;
which is called Anti-Stokes Raman scattering. • Quantum mechanically Stokes and Anti-Stokes areequally likely processes. However, with an ensemble of molecules, the majority of molecules will be in the ground vibrational level (Boltzmann distribution) and Stokes scatter is the statistically more probable process. As a result, the Stokes Raman scatter is always more intense than the anti-Stokes and for this
reason, it is nearly always the Stokes Raman scatter that is measured in Raman spectroscopy. Raman spectroscopy is used in chemistry to identify molecules and study chemical bonding and intramolecular bonds.In solid-state physics, Raman spectroscopy is used to characterize materials, measure temperature, and find the crystallographic orientation of a sample . In nanotechnology, a Raman microscope can be used to analyze nanowires to better understand their structures, and the radial breathing mode of carbon nanotubes is commonly used to evaluate their diameter.
This content was presented by me in Sathayabama University, India as an Invited talk in a DBT sponsored training program which covers the generalized about the Raman Scattering technique.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
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Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
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1. TOPIC – COHERENT ANTI-STOKES
RAMAN SPECTROSCOPY (CARS)
S.P.C. GOVT. COLLEGE , AJMER
SEMINAR SESSION : 2021-22
SUBMITTED TO : DEPARTMENT OF CHEMISTRY
SUBMITTED BY : ANKIT JOSHI
M.Sc. PREVIOUS CHEMISTRY SEMESTER – 2nd
2. CONTENTS :-
Introduction
Theoretical Background
Some Basics Of Rayleigh And
Raman Scattering
Coherent Anti-Stokes Raman Spectroscopy
(CARS) :-
CARS Process
Advantages of CARS
Limitations of CARS
Applications of CARS
Summary
3. Introduction
A spectroscopic technique based on coherent anti-Stokes
Raman scattering (CARS) was first demonstrated by Maker
and Terhune in 1965.
CARS spectroscopy is a powerful technique which has been
widely applied essentially in interdisciplinary research fields on
the borders of biology, chemistry, physics, healthcare, defense,
remote sensing, forensics, material science and so on.
The recent breakthrough achievements such as detection
bacterial spores, implementation of coherent Raman
microscopy, gas-phase thermometry of reacting and non-
reacting flows and many others have been its state-of-art
successes.
4. Theoretical Background
We have read earlier that the probability or relative intensity of Rayleigh
lines, stokes and anti-stoke lines occurs inside solutions are in 1:10−3
:10−6
ratio.
Anti-stock lines have the least probability of occurring in the solution
because when the ground state falls bellow the original level in the anti-stokes
lines, its probability decreases. And when we take its signal, it fails.
Thus anti-stoke lines are so weak that’s why we cannot study it with the help
of normal Raman spectroscopy, So we need coherent anti-stokes Raman
spectroscopy (CARS).
A simple comprehensive theory for CARS is introduced in this PPT. It
begins with CARS formulation and, based on obtained solutions, a newly
recognized (somewhat neglected in the past) effect such as enhancement in
coherent Raman spectroscopy at positive probe delay is introduced in detail.
At the end of this section, the experimental observations are elucidated with
the CARS formulation.
5. SOME BASICS OF RAYLEIGH AND
RAMAN SCATTERING
The source of energy in Raman spectroscopy is laser, so
laser is used in Raman spectroscopy.
Scattering of light – When sunlight
enters the atmosphere of the earth.
The atoms and molecules of different
gasses present in the air absorb the
light. Then these atoms re-emit light
in all directions. This process is known
as scattering of light.
The atoms or particles that scatter light are called scatters.
Radiation – Radiation is energy or particles that comes
from a source and travel through space at the speed of light.
6. TYPES OF SCATTERING
𝟏. Elastic scattering 2. Inelastic scattering
If the energy of the
incident beam of
light and the
scattered beam of
light are same, then
it is called as ‘elastic
scattering’.
If the energy of the
incident beam of light
and the scattered
beam of light are not
same, then it is called
as ‘inelastic
scattering’.
7. 𝑹𝒂𝒚𝒍𝒆𝒊𝒈𝒉 scattering Raman scattering
Rayleigh scattering is the elastic
scattering process in which the
electromagnetic radiation is
elastically deflected by particles
of matter, without a change of
frequency but with a phase
change.
Raman scattering is the
inelastic scattering of photons
by matter, meaning that there is
both an exchange of energy and
a change in the light’s direction.
Raman Stokes scattering
When the energy of the
scattered photons is less than
the incident photons, the
scattering is known as Raman
Stokes scattering.
When the energy of the
scattered photons is more than
the incident photons, the
scattering is known as Raman
anti-Stokes scattering.
Raman anti-Stokes scattering
9. Coherent Anti-Stokes Raman Spectroscopy
(CARS) :-
In this technique of coherent anti-Stokes
Raman spectroscopy (CARS), two sufficient
laser beams of high intensity with frequency
υ1 and υ2 are focussed on a sample. Mixing
in the sample generates a new coherent beam
of low intensity at a frequency 2υ1- υ2= υ3.
υ1 + υ1 − υ2 = 2υ1 − υ2
If frequency υ1 is fixed and the value of
frequency υ2 is varies such that :
υ1-υ2=υR
Then the scattered radiations are occurs
i.e. υ1+υR=υ3
Where υ1 = Incident radiations frequency
υ2 = Transmitted radiations frequency
υR = Raman active vibrational of molecular
system
υ3 = Relative frequency in υ1 Or Anti-stoke
Raman frequency
10. The relative radiation frequency υ3 of υ1 is the anti-stokes
Raman radiation. Which is very intense and paired. This is
called coherent anti-stokes Raman spectroscopy (CARS).
The intensity of a Raman spectrum can be increased by CARS.
This technique is based on the fact that if two laser radiation
whose frequency are υ1 and υ2, is passed through a sample. So
they are paired in such a way that the coherent frequencies of
the different values can be obtained.
One of these frequencies can be written as :-
υ’ = 2υ1 - (υ1 - Δυ)
υ’ = υ1 + Δυ
This frequencies is the corresponding frequency of the anti-
stokes line. In this way, coherent radiation of high intensity
will be obtained which are called coherent anti-stokes
Raman spectroscopy (CARS).
11. CARS Process
The CARS process consists of
two coherent laser radiation beams
υ1 and υ2 , which are almost collinear
in the molecular medium.
If the frequency υ2 of the other
beam is varied by keeping the
frequency υ1 constant of one beam.
Then the frequency difference between the two beams come.
Which is equal to Raman shift υR.
Due to which a third beam υ3 is produced which is called
coherent anti-stokes Raman spectroscopy (CARS).
12. This is almost parallel to the incident beam(υ1) and
It is also paired with them.
υ3 = υ1 + (υ1-υ2)
= 2υ1 - υ2
or υ3 = υ1 + υR
The υ3 beam can be separated from the incident
beam (υ1) by filtering.
The CARS process depends on the square of the
normal Raman scattering and the square of the
number of molecules.
13. Advantages of CARS
I. CARS signals are stronger by 8-10 orders of magnitude than
normal Raman experiment.
II. CARS signal can be easily visualized compared to
fluorescence.
III. Scattering intensity is increase enormously. ( It is non linear
technique. It reveals high resolution which is determined by
line width of lasers.
IV. Even microquantities (10−5- 10−7) can be detected by
resonance CARS.
V. High Raman conversion efficiencies are obtained.
VI. Excellence collection efficiency is possible since CARS is
generated as a beam.
VII. Narrow spectra are obtained without the need for a
monochromator.
14. Limitations of CARS
I. Requires complicated set up, difficult adjustment
costly equipment.
II. Spectra evaluation is non-trivial.
III. Band shapes are often distorted.
IV. Samples may decompose by high power laser beam
focusing.
V. Signal fluctuation are caused by frequent
instabilities of the lasers.
VI. No quantitative conclusion can be drawn from
signal intensity.
15. Applications of CARS
I. Molecular structure determination is important tool.
II. To study the rotational spectrum of gases. Even difference between υrot.
& υvib. and derivation from Boltzmann distribution can be analysed.
III. Gas phase combustion process are mostly studied by CARS. (CO2, CO,
O2, N2, CH4, H2O, H2 etc. in flames can be studied).
IV. Excellence technique for studying biological samples in aqueous
solution which often produce strong fluorescence in normal Raman
scattering.
V. Enhancement of CARS signals occurs of radiation approach the
electronic absorption frequency of the system.
VI. Medicinal samples like ferrocytochrome, cyanocobolamin have been
studied in dilute (10−5M) aqueous solution.
VII. Numerous application of CARS in molecular beam studies energy
transfer and plasma diagnostics are excepted.
16. Summary
This ppt presented a brief overview to the basics of coherent anti-
Stokes Raman spectroscopy. First we introduced the CARS technique
and its strengths and barriers. Namely, we presented the integral
formulae for coherent anti-Stokes and Stokes Raman scattering, and
discussed the closed-form solutions, its complex error function, and
the formula for maximum enhancement of the inferred pure coherent
Raman spectra. The time-resolved coherent Stokes Raman scattering
experimental observations were also quantitatively elucidated as an
example. Moreover, various experimental realizations of narrowband
probe pulses were illustratively explained. Finally, several experimental
data were presented and discussed based on all Gaussian approach
presented in this review. Understanding the essentials of coherent
Raman spectroscopy promotes importance of a number of experiments
including the ones utilizing a broadband excitation with a narrowband
delayed probing for successful background suppression emphasized in
this work.