Electron spin resonance (ESR) spectroscopy involves exposing paramagnetic substances containing unpaired electrons to microwave radiation, causing transitions between the electron spin energy levels. ESR provides information about unpaired electrons and their chemical environment. The ESR spectrum of hydrogen atom appears as a doublet due to interaction between the unpaired electron and nuclear spin of hydrogen. More complex spectra result from interactions between unpaired electrons and multiple nuclear spins. ESR is used to study paramagnetic species and identify unpaired electrons in compounds.
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
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
NQR - DEFINITION - ELECTRIC FIELD GRADIENT - NUCLEAR QUADRUPOLE MOMENT - NUCLEAR QUADRUPOLE COUPLING CONSTANT - PRINCIPLE OF NQR - ENERGY OF INTERACTION - SELECTION RULE - FREQUENCY OF TRANSITION - APPLICATIONS
Partition function indicates the mode of distribution of particles in various energy states. It plays a role similar to the wave function of the quantum mechanics,which contains all the dynamical information about the system.
It contains the basic principle of Mossbauer Spectroscopy.
Recoil energy, Dopler shift.
The instrumentation of Mossbauer Spectroscopy.
Hyperfine interactions.
NQR - DEFINITION - ELECTRIC FIELD GRADIENT - NUCLEAR QUADRUPOLE MOMENT - NUCLEAR QUADRUPOLE COUPLING CONSTANT - PRINCIPLE OF NQR - ENERGY OF INTERACTION - SELECTION RULE - FREQUENCY OF TRANSITION - APPLICATIONS
Partition function indicates the mode of distribution of particles in various energy states. It plays a role similar to the wave function of the quantum mechanics,which contains all the dynamical information about the system.
It contains the basic principle of Mossbauer Spectroscopy.
Recoil energy, Dopler shift.
The instrumentation of Mossbauer Spectroscopy.
Hyperfine interactions.
Presented Presentation on college level about Raman spectroscopy where I describe about Principle and phenomena and their instrumentation and applications to chemistry.
electron pairing and mechanism of superconductivity in ionic crystals Qiang LI
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Analyses are first made to a one-dimensional long ion lattice chain model (EDP model), with the presence of lattice wave modes having frequency ω. A mechanism of electron pairing is established.
Analyses are then extended to scenarios of 3D ionic crystals, particularly those with a donor/acceptor system, with emphasis being given to the interpretation and understanding of binding energy of electron pairs formed between electrons at the top/bottom of donor/acceptor band and the bottom/top of conducting/full band.
It is established that once the lattice/EM wave modes are established in its range, which can be long or even macroscopic, electron pairs are produced in the crystal’s electron system over the same range by stimulated transitions induced by the EM wave mode. The lattice wave mode having the maximum frequency ωM is of special significance with respect to superconductivity, for electron pairs produced by it can be stabilized in the context of a combination of some special factors (including energy level structure featured by donor/acceptor band and ωM) with a binding energy typically no smaller than hωM/(2π). A candidate mechanism of electron pairing in ion crystals and therefore of superconductivity is provided.
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This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
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It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
5. ELECTRON SPIN RESONANCE
SPECTROSCOPY
DEFINITION:
ESR is a branch of absorption
spectroscopy in which radiation
having frequency in the microwave
region is absorbed by paramagnetic
substances to induce transition
between magnetic energy levels of
electrons with unpaired spins.
7. • ESR spectra observed in microwave
region of the electromagnetic
radiation.
• ESR observed primarily in systems
containing unpaired electron.
• COMPARISION BETWEEN NMR and
ESR
9. • Which molecules possessing
electrons with unpaired spins.
This phenomenon has been
designated by different names,
1. Electron paramagnetic
resonance(EPR)
2. Electron spin resonance(ESR)
3. Electron magnetic resonance(EMR)
10. • Now I discuss basic aspects of
ESR
i) Hyperfine splitting
ii) Applications
11. ESR theorem
• Electron spin s=1/2 spin angular
momentum quantum number
can have value of ms=±1/2.
• Presence of magnetic field this
degeneracy resolved, low
energy state ms=-1/2 in aligned
applied field high energy state
ms=+1/2 in opposed applied
field. E=h=gHo
12. How does EPR Work?
Like a proton, an electron has a spin, which gives it a
magnetic property known as a magnetic moment.
When an external magnetic field is supplied, the
paramagnetic electrons can either orient in a direction
parallel or antiparallel to the direction of the magnetic field
.
This creates two distinct energy levels for the unpaired
electrons and measurements are taken as they are driven
between the two levels.
13. The EPR experiment
• Put sample into
experimental magnetic
field (B)
• Irradiate (microwave
frequencies)
• Measure absorbance of
radiation as f(B)
Weil, Bolton, and Wertz, 1994, “Electron Paramagnetic Resonance”
16. Principles of EMR spectroscopy
B 0
DE
h
Classical theory:
Electron spin moment interacts with
applied electromagnetic radiation
m s = —
1
2
m s = —
1
2
-
Energy
Quantum theory:
transitions between energy levels
induced by magnetic field
Resonance condition
h = gmBB0
17. The hyperfine effect
• The magnetic field experienced by the unpaired electron
is affected by nearby nuclei with non-zero nuclear spin
Weil, Bolton, and Wertz, 1994, “Electron Paramagnetic Resonance”, New York: Wiley Interscience.
18. Hyperfine splitting of EPR spectra
• The magnitude of the splitting and the number of lines
depend upon:
– The nuclear spin of the interacting nucleus
• # of lines = 2n(I + ½) so I = ½ gives 2 lines, etc.
– The nuclear gyromagnetic ratio
– The magnitude of the interaction between the
electronic spin and the nuclear spin
• Magnitude of the splitting typically decreases
greatly with increasing numbers of bonds between
the nucleus and unpaired electron
19. 10 Gauss
No hyperfine
1H)
14N)
2 identical I=1/2 nuclei
1 I=5/2 nucleus (17O)
Hyperfine coupling
If the electron is surrounded by n spin-
active nuclei with a spin quantum
number of I, then a (2nI+1) line pattern
will be observed in a similar way to
NMR.
In the case of the hydrogen atom (I= ½),
this would be 2(1)(½) + 1 = 2 lines.
20. Some nuclei with spins
Element Isotope Nuclear No of %
spin lines abundance
Hydrogen 1H ½ 2 99.985
Nitrogen 14N 1 3 99.63
15N ½ 2 0.37
Vanadium 51V 7/2 8 99.76
Manganese 55Mn 5/2 6 100
Iron 57Fe ½ 2 2.19
Cobalt 59Co 7/2 8 100
Nickel 61Ni 3/2 4 1.134
Copper 63Cu 3/2 4 69.1
65Cu 3/2 4 30.9
Molybdenum 95Mo 5/2 6 15.7
97Mo 5/2 6 9.46
21. • Electron Paramagnetic Resonance of
Hydrogen Atom
It contains an unpaired electron with S = 1/2 and a
proton with nuclear spin I = 1/2 (ms = ±1/2 and mI =
±1/2). In the absence of magnetic field (B0 = 0), the
electron spin energy levels are degenerate, i.e., have
the same energy (F Application of B0 lifts the
degeneracy between them (the ms = −1/2 sublevel
going down and the ms = +1/2 sublevel going up).
Each of these electron sublevels further interacts with
the nucleus (I = 1/2) giving four sublevels designated
by the value of mI. This phenomenon is called
hyperfine splitting.
22. Hyperfine splittings multiply with
the number of nuclear spins
O
.
O-
H
H
H
H
Benzoquinone anion radical:
1 proton – splits into 2 lines 1:1
2 protons split into 3 lines 1:2:1
3 protons split into 4 lines 1:3:3:1
4 protons split into 5 lines 1:4:6:4:1
-60 C
20 C
At higher temperature:
faster motion - sharper lines
shorter lifetime - smaller signal
23.
24. It contains an unpaired electron with S = 1/2 and
three equivalent protons. Each proton has a spin
I = 1/2. Therefore, the total nuclear spin is I = 3/2.
For each ms = ±1/2, the mI values
are +3/2, +1/2, −1/2, −3/2 as shown in Fig. The
interpretation of the ESR spectrum is similar to that
of H atom. The ESR spectrum shows four equally
spaced lines, (n + 1), i.e., a quartet in the intensity
ratio 1:3:3:1. The spacing between any two
successive lines represents the constant (A)
isotropic coupling
Methyl radical CH3 radical
25. APPLICATIONS
• The site of unpaired electrons.
• The no. of line compounds decide about
the no. and type of nuclei present in the
neighboured of the odd electron.
• The ESR spectrum the value of g can be
measured by comparing the position of
the line with that of a standard
substance of known g value. ex DPPH
powder.
• The electrical field is not spherical.