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Unformatted text preview: functional group region fingerprint region wavelength ( ) frequency ( ! ); cm-1 %T 100 A 100 Infrared spectrogram Recorded linear in wavelength better for ID Old style grating instrument - changed gears each part is linear in wavelength hexane Strong peak Weak peak Characteristics of an IR Spectrogram - linear in wavelength Infrared Spectrum 2 functional group region fingerprint region frequency ( ! ); cm-1 100 A There are two horizontal scales, one in cm-1 (the frequency scale, ! ) and the other in (the wavelength scale in microns or micrometers, which is 10-6 meters). There are also two vertical scales: absorbance (A) and % transmittance (%T). If all of the infrared light is absorbed by the molecule, the value of A = 100%, which means that no light is transmitted, and %T = 0. If no light is absorbed by the sample, there is 100% transmittance (%T = 100) and 0% A. A larger value of A is associated with a stronger peak and a smaller value of A with a weaker peak. That region between 4800-1400 cm That region between 4800-1400 cm 1 is called the is called the functional group region functional group region and the region and the region between 1400-400 cm between 1400-400 cm 1 is called the is called the fingerprint region fingerprint region...
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- Fall '08