Spectroscopy Photoelectron spectroscopy X-ray absorption spectroscopy.
Spectroscopy Absoption
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Transcript of Spectroscopy Absoption
Degrees of Freedom
Rotational Spectroscopy
Electronic Transitions
Vibrational Spectroscopy
microwave infrared
Interaction with matter Energy levels
Spectroscopy
Absorption Spectroscopy Emission Spectroscopy
Introduction to Matters
Rotational Spectroscopy
Vibrational Spectroscopy
Absorption and emission Spectroscopy
Lakowicz, “Principles of Fluorescence Spectroscopy”, Springer Publishers, 3rd Edition, 2011
Atkins, Physical Chemistry, 9th edition, 2009
Banwell & McCash, Fundamentals of Molecular Spectroscopy, 4th edition, 1996
Moog, Spencer and farrell, Physical Chemistry: A Guided Inquiry: Atoms, Molecules,
and Spectroscopy, 2003
• The sun produces a full spectrum of electromagnetic
radiation
http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html
http://kr.blog.yahoo.com/bmw26z/2188
Components of Electro Magnetic
Radiation
v
Two Components of EM
Radiation • Electrical field (E): varies in magnitude in a direction
perpendicular to the direction of propagation
• Magnetic field (M): at right angle to the electrical
field, is propagated in phase with the electrical field
• Wavelength (l), distance from one wave crest to another
• Frequency (n), No. of crests passing a fixed point/ given time
• Amplitude, height of each peak (watts/sq. meter
• The speed of EM energy “c” 300,000km/second,
c = nl where l and n are inversely related
Interaction of radiation with matter
• If there are no available quantized energy levels matching the quantum
energy of the incident radiation, then the material will be transparent to that
radiation
Wavelength
Molecular Transitions
for UV-Visible Absorptions
• What electrons can we use for these
transitions?
Nature of Shift Descriptive Term
To Longer
Wavelength Bathochromic
To Shorter
Wavelength Hypsochromic
To Greater
Absorbance Hyperchromic
To Lower
Absorbance Hypochromic
Absorption and Emission Spectroscopy
Reflection and Scattering Losses
Introduction to Absorption
LAMBERT-BEER LAW
ionconcentrat
pathlength
tyabsorptivi
loglog0
0
c
b
a
kcabcA
P
PTA
P
P
P
PT
solvent
solution
Power of
radiation after
passing through
the solvent
Power of radiation
after passing
through the sample
solution
Problems
23 CY 515 (Spectroscopic Method of Analysis)
Dr. Priyabrat Dash
NIT Rourkela, India
Beer’s law and mixtures • Each analyte present in the solution absorbs light!
• The magnitude of the absorption depends on its e
• A total = A1+A2+…+An
• A total = e1bc1+e2bc2+…+enbcn
• If e1 = e2 = en then simultaneous determination is
impossible
• Need nl’s where e’s are different to solve the mixture
Spectral nomenclature of shifts
Electronic Transitions in Molecules
Molecular Orbital (MO) Theory
for C2H4 molecule,
UV or Visible
spectral region
Department of Chemistry, KAIST
Fate of Excited Electronic States
Molecular Motion and Spectroscopy
Study of Interaction of Matter and Light (Photon)
• Molecular Spectroscopy
Information about molecules such as geometry and energy
levels are obtained by the interaction of molecules and photons
• Molecular motions: Translation, Rotation, Vibration
determines the energy levels for the absorption or emission of
photons
Electronic, Vibrational, and Rotational Energy Levels
of a Diatomic Molecule
Exercise: Indicate the
molecular state in which it is
electronically in the ground
state, vibrationally in the first
excited state, and rotationally
in the ground state.