Regions

abbreviation	name	wavelength	wavenumber (cm)
NIR	near IR	700 nm-2m	14,000-5,000 cm
MIR	mid IR	2 m-25 m	5,000-400
FIR	far IR	25 m-1 mm	400-10
VFIR	very far IR
submm	submillimeter
microwave

Range (nm)	Mode
500	Fe+2 spin-forbidden (very weak)
550-650	Fe+3 ()
650-750	Fe+3 ()
900	OH 3-stretch
900-1000	Fe+2 (undistorted 1000 nm)
1150	H2O 2-stretch+bend
1400	OH 2-stretch, H2O
1700	CO3 vibrational overtones
1800-2000	Fe+2
1935	H2O stretch+bend (6223 nm = 1607 cm + 2808 nm
	= 3561 cm 5168 cm = 1935 nm)
2200	CO3 vibrational overtones
2300	X-OH vibrational mode
2350	CO2 asymmetrical stretch
2700-2900	OH 1-stretch
2808	H2O stretch
6223	H2O bending
7000	CO3 asymmetric stretching
8500	SO4 stretching mode
9400	PO4 stretching mode
2.9	OH
3.0	broad H2O
3.4	CH (organic contaminant)
5.9	H2O
6.2	CO3 asymmetric stretch
8-11	asymmetric SiO4 stretch modes (wide)
11	CO3 overtone
14	CO3 overtone
15-16	SO4, PO4
20	lattice modes

Properties of infrared spectra follow. Multiple peaks of different intensities for a single line implies that geometrically distorted sites must be present. An examination of an infrared spectrum therefore contains information about the nature of the nature of the crystal site. The position of the OH stretch frequency can be tabulated as a function of the OH-O bond distance. This technique does not work with bent H bonds or with multiple hydrogen bonds, however. Combination stretch+bending modes can sometime also be observed in a more convenient region of the spectrum than the individual stretch and bend.

To prepare a sample, grind it into a powder with particle size less than a wave length. An "infrared light bulb" called a glo-bar is used as the source. The powder in then embedded in a material with the same refractive index at infrared wavelengths. For organic chemicals with index of refraction (), mineral oil is used. A KBr pellet may also be used (), but it is hygroscopic and so must be kept in dessication. TlBr can also be used for high n substances (), but it is highly toxic.