The mid-infrared region covers the frequency range of 3x10^12 to 1.2x10^14 Hz and wavelengths between 2500 and 20000nm. The technique is used for chemical analysis and is based on diffuse-reflectance. The soil sample is illuminated with a broadband light source the light is absorbed by increasing the vibration energy of molecular bonds. Absorption occurs at specific frequencies based on the bond characteristics (i.e. geometry, strength and atomic mass). The mid-infrared region contains information on soil mineral and organic composition with fundamental molecular vibrations of soil components occurring in this band.
MIR spectroscopy can be used to measure a range of soil properties such as water content, carbon, nitrogen, texture (clay minerals), iron oxides etc.
Portability is limited.
1. Janik, L.J., Merry, R.H., Skjemstad, J.O., 1998. Can mid infra-red diffuse reflectance analysis replace soil extractions? Australian Journal of Experimental Agriculture, 38(7): 681-696.
2. Viscarra Rossel, R. A., Walvoort, D. J. J., Mcbratney, A. B., Janik, L. J. & Skjemstad, J. O. (2006) Visible, near infrared, mid infrared or combined diffuse reflectance spectroscopy for simultaneous assessment of various soil properties. Geoderma, 131(1-2), 59-75.