Raman Spectroscopy

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Raman Spectroscopy
Chapter 18
CHM 411
Spring 2013 Suroviec
I. Introduction
• Radiation when passed
through a transparent
medium is scattered.
II. Theory
• Acquired by irradiating the
sample with a laser of
visible/Near IR radiation
B. Mechanism
• In Raman excitation is normally
carried out by radiation well away
from absorption peaks to avoid
fluorescence
• The most likely is Rayleigh
scattering
• This process is NOT QUANTIZED –
therefore depending on the
frequency of the radiation from
the laser source, the energy of
the molecule can assume any
virtual state between the ground
state and the first electronic state
B. Mechanism
• For a given bond the energy shifts
in Raman should be identical to
the energies of its IR absorption
bands only if the vib modes are
both IR and Raman active
• IR: requires change in dipole
moment
• Scattering: momentary distortion
of the electrons distributed
around a bond, followed by
reemission of the radiation as the
bond returns to ground
C. Instrumentation
D. Applications
1. Inorganic Species
2. Organic species
3. Biological Applications
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