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Howard Mark (hlmark)
Senior Member
Username: hlmark

Post Number: 462
Registered: 9-2001
Posted on Thursday, December 01, 2011 - 3:13 pm:   

Fernando - the mid-IR region covers wavelengths from roughly 2.5 microns (2500 nm, 4000 cm-1) at the short-wavelength end, and at the long wavelength end somewhere between 20 microns (20,000 nm, 500 cm-1) to 50 microns (50,000 nm, 200 cm-1), the exact value depending on the details of the instruemntation available.

485 cm-1 is thus clearly at the long-wavelength end of the mid-IR region, in fact it verges on being considered far-IR by most chemists and spectroscopists.

The reason you have difficulty finding information about absorbaces below 485 cm-1 is because there are very few of them. It would involve the vibrations of very heavy atoms held in molecules by weak bonds, indeed, and those would tend to be weak absorbances. Also absorbances in the far-IR would be more likely to involve molecular rotations rather than vibrations, and not many chemists/spectroscopists are familiar with the characteristics of those. I would suggest you search the literature for information on far-IR spectroscopy and if you find any recent published papers, that you contact the authors of those papers for information.

Howard

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Fernando Morgado (fmorgado)
Senior Member
Username: fmorgado

Post Number: 30
Registered: 12-2005
Posted on Thursday, December 01, 2011 - 1:42 pm:   

Hello :
I know is a NIR discussion group and not a MID discussion group, but maybe some people can help to me. I need to know wich can be the importance of information below 485 cm-1. I intent find who bonds absorb in this area but I can not find it.
Thanks in advance

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