For a molecule to absorb infrared radiation it must undergo a net
change in dipole moment as a result of vibrational or rotational
motion.
Vibrations can be subdivided into two classes, depending on
whether the bond length or angle is changing:
stretching (symmetric and asymmetric)
bending (scissoring, rocking, wagging and twisting)
The energies associated with rotational transitions are generally
much smaller than that for vibrational transitions and the peaks
are found below 300 cm-1. Typically, vibrational spectra are
measured between 4000 cm-1 to 650 cm-1 for NaCl optics or 4000
cm-1 to 450 cm-1 for KBr optics.
These vibrational types can be demonstrated by selecting the
buttons below:
Return to Index of IR
files.
Some interpreted spectra that use CHIME
for display of both IR and molecular structure have been
generated. (WINDOWS only).
A useful tutorial on IR spectroscopy can be found at CSU
Stanislaus. IR
pages on the Web are maintained at the College of Pharmacy at
the University of Kentucky. Return to Chemistry, UWI-Mona,
Home Page
Created and maintained by Dr. Robert J.
Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created Dec 1998. Last modified 22nd February,
2000. URL
http://wwwchem.uwimona.edu.jm:1104/spectra/iranim/irmodes.html
Return to Chemistry, UWI-Mona,
Home Page
Created and maintained by Dr. Robert J.
Lancashire,