3. OUTLINES
• DEFINATION
• ELECTROMANETIC RADIATION
• ELECTROMAGNETIC SPECTRUM
• REGIONS IN ELECTROMAGNETIC SPECTRUM
• BASIC PRINCIPLE AND THEORY
SPECTROSCOPY
4. SPECTROSCOPY
Deals with emission as well as
absorption spectra.
OR
The interaction b/w the matter and
electromagnetic radations.
5. What is Light?
Light is a form of energy.
Light travels through space at extremely
high velocities.
The speed of light (c) ~ 3 x 1010 cm/sec or
186,000 miles per second.
6. WHAT IS ELECTROMAGNETIC RADIATION
.Light is classified as electromagnetic
radiation (EMR).
• EMR can be described as wave with
properties of wavelength, frequency, velocity
and amplitude.
• EMR can be treated as discrete packets of
energy or particles called photon or quanta.
7. Radiation is a form of energy. There are two
basic types of radiation. One kind is
particulate radiation, which involves tiny
fast-moving particles that have both energy
and mass. Particulate radiation is primarily
produced by disintegration of an unstable
atom and includes Alpha and Beta particles.
8. The second basic type of radiation is
electromagnetic radiation. This kind of
radiation is pure energy with no mass and is
like vibrating or pulsating waves of electrical
and magnetic energy.
9. Characteristics of Light
Light behaves like a wave.
– That is, it can be modeled or characterized with wave like
properties.
Light also behaves like a particle.
– The photon and photoelectric effect.
Today, we envision light as a self-contained packet
of energy, a photon, which has both wave and
particle like properties.
10. ELECTROMAGNETIC SPECRUM
• The arrangement of all types of
electromagnetic radiation in order of
increasing wavelengths or decreasing
frequencies is known as complete
electromagnetic spectrum
15. X- rays
X-rays is a form of electromagnetic
radiation. Most X-rays have a wavelength
in the range of 0.01 to 10 nanometers.
x rays also called Rontgen radiation
because is discovered by Rontgen
16. X- Ray Tube Principles
• Artificially X- rays are produced by decelerating high-velocity
electrons. The apparatus, called X-ray tube,
therefore has a source of electrons, a means of
accelerating them to high velocities and something to
stop them so that they lose their energy.
• The electron source is the cathode, heated by a
filament. The heated cathode emits electrons.
• The anode has a positive voltage (thousands of volts)
and attracts the electrons so that they reach a high
velocity.
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18.
19.
20.
21. Infrared spectroscopy
• Any compound having covalent bonds,
whether organic or inorganic, absorbs various
frequencies of EMR in the infrared region of
the electromagnetic spectrum.
• IR region lies at wavelengths longer than
visible light (1nm), but lies at wavelengths
shorter than microwaves (1mm
22. • The term infrared “IR” comes the range of the EMR
spectrum between 0.78-1000 μm or 12800-4000
cm-1.
• It is useful to divide the IR region into three
sections, near IR, mid IR and far IR.
Region
Wavelength (μm) Wavenumber (cm-1)
Near 0.78-2.5 12800-4000
Mid 2.5-25 4000-400
Far 25-1000 400-10
23. UV/VISIBLE SPECTROSCOPY
• The absorption of uv/visible radiations
which is associated with the excitation
of valence electrons from ground state
to higher energy states.
• It is also called electronic spectroscopy
b/c there is electronic excitation due
the absorption of uv/visible light
24. Why uv /visible spectroscopy
discussed together
• Uv/visible discus together because both have
same basic principle and leads to the same
type of molecular excitation.
• Range of uv/visible
• uv ==== 10 to 400 nm
• Visible ====== 400 to 800 nm
26. Absorption of radiations and
electronic transitions
• The absorption of uv/visible
radiations by molecules is
associated with excitation of
valence electrons from the
ground state to higher energy
states.
27.
28. Transitions
This transitions occur in saturated hydrocarbons,
which contain only strongly bound sigma
electron.
The excitation of these electrons from a sigma
orbital to a sigma star orbital require a large
amount of energy absorption in the vacuum uv
regions.
29. n Transitions
• Saturated compounds containing atoms with
lone pairs (non-bonding electrons) are capable
of n transitions. These transitions
usually need less energy than
transitions. They can be initiated by light
whose wavelength is in the range 150 - 250 nm.
• The number of organic functional groups with
n peaks in the UV region is small.
30. n and Transitions
• Most absorption spectroscopy of organic
compounds is based on transitions of n or
electrons to the excited state.
• These transitions fall in an experimentally
convenient region of the spectrum (200 - 700
nm). These transitions need an unsaturated
group in the molecule to provide the
electrons.
31. Terms describing UV absorptions
• CHROMOPHORE:
Any structural feature present in a molecule
that is responsible for the absorption of
electromagnetic radiation and hence for
imparting colour to a compound is known is
chromophore
33. 2Auxochromes: substituents with unshared pair
e's like OH, NH, SH ..., when attached to π
chromophore they generally move the
absorption max. to longer λ.
3. Bathochromic shift: shift to longer λ, also
called red shift.
4. Hysochromic shift: shift to shorter λ, also
called blue shift.
5. Hyperchromism: increase in ε of a band.
6. Hypochromism: decrease in ε of a band.
36. ACKNOWLEDGEMENT:
I am very thankful to ALLAH PAK, for His Divine
support. Then dedicated to my Loving Parents. But I
have no words to acknowledge for their unconditioned
support and courage .At last but not the least I offer
my heartiest gratitude to my
Respected and honorable Dr: Prof:Amber solangi
Whose valuable suggestions and guidance capable me
to made this effort possible.
And also our colleagues.
