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Chapter III CHN Analysis, FT IR …..
Obviously, these are present in pure and amino acids doped KDP crystals. It
is also interesting to note that P=O stretching vibration frequency practically
remains unaltered for all crystals; notwithstanding , the frequencies of O=P-
OH symmetric stretching and O-P-OH symmetric stretching vibrations of
doped KDP crystals decrease with respect to pure KDP , which indicates the
interaction of amino acids with KDP through hydrogen bonds of the particular
groups. At the same time, the absorptions due O=P-OH bending exhibit larger
values for amino acids doped crystals and the pure KDP crystals , which also
further hints the interaction of amino acids with KDO through hydrogen bond.
The force constant of particular diatomic atoms can be calculated from
the particular absorption peak in FTIR spectrum. Considering a molecular
model, where the nuclei are presented by point masses and the inter-atomic
bonds as mass less spring which follows the Hooke’s law, the vibrations
changes the inter atomic distance sinusoidally but the center of gravity
remains the same. Therefore, at any time during the vibrations the atomic
displacements are inversely proportional to the masses. If masses are
expressed in the unified atomic masses (u) and the force constant is m-
dyne/Å [1].
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1
F
M
Where, 1303 is equal to (NA X 10 5 ) 1/2 / (2C)
NA - Avogadro’s number, F - force constant.
1
.. 1303 ....
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....
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142
(3.1)
By taking into account this simple model, the force constant for O-H
vibrations at 3600 cm -1 was found to be 7.2 is m-dyne /Å [1]. In the present
study, the force constants for O-H bond are calculated for pure and various
1
M
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